I personally wouldn't buy these again now (that I know more about audio) than $75 new. However, these are my first headphones, and I have some sentimental attachments to them. I actually prefer these to my HE-5/EF-5 currently, though unfortunately it is down and I can't do a perfect A/B comparison for now.

I wouldn't recommend anyone to get these now, but these were the first phones I toted to school and convinced three of my friends to purchase decent audio. All of them have gotten Senns (two of them with the HD555s - one used, the other I will sell mine to, the other with a very similar PC 350, which is probably not any better, unfortunately). I do hope that they will also eventually move on and see even further up the chain, not necessarily relegated to Sennheiser's offerings (not an insult to these, I love them).
 
SQ wise, they do everything I need them to. Easy to drive, without fatiguing bass, though I'd prefer to have some more isolation for portable listening (will try ES-10s as the sole HP for both home and portable, though there is a good chance that may not work too).
 
In a nutshell, they have good SQ for the price, but they aren't the creme of the crop any more at the price range. However, I've had extremely positive experiences with comfort and build quality. These are supremely comfortable and I don't even notice them on much of the time. I leave them always even when I'm not playing anything. The velvety-like pads are also great for a slight bit of insulation on a cold day (though on the flipside, they are bad in heat over 28-30C, though that is infrequent in Vancouver, Canada).

They also appear to be indestructible to me. Throw in a few hundred hours of moderate to extreme rain, much use both indoors and out, being dropped several dozens of times, slammed, dropped from relatively high perches, hitting concrete and other hard surfaces, having its gold plated connector bent out of shape half a dozen times, and still working strong - that is simply incredible. Not everyone has had such a positive experience in this department, but I absolutely adore them for this and they will always hold sentimental value to me. I hope the future owner of my pair of HD 555s treats and enjoys them well.
 

Edit: For the purchase date, I believe I bought it in May 2008, give or take a month. Also edited ratings a bit to be a bit more fair.
 
Edit 2: A lot of owners complain about issues with build quality, which is another reason why I would never suggest anyone to buy these phones now, with better options for whatever use you may have for these unless you can get these for under $100, preferably in the 70s range. However, the unsatisfied are always the more vocal bunch, and this has been perfect for me in my 2 years of extreme abuse (no kidding).

Edit 3: A (possibly) final append to my review - despite the low impedance and high sensitivity, these are NOT the definition of easy to drive. Yes, they are very easy to drive at home, and both my Auzentech X-Fi Prelude & Nuforce uDac will drive them to their potential, but they will NOT sound good straight out of an iPod or DAP (in my case, a Cowon S9) [Actually, the uDac does a much better job, as the Prelude botches the bass, has worse separation and sounds more veiled and muddy]. Look for phones made specifically for portable in this case - a 3 M cable, a 1/4" to 1/8" adapter plus sub-optimal sound quality overall is atrocious for outside usage, not to mention excessive sound bleeding and nearly no isolation (they're open cans, after all). ES-10s, in contrast, are excellent even when driven straight out of a DAP with no external (even portable) amplification or DAP, and I actually prefer the sound signature out of my S9 over my uDac.
 
ES10s of course, also do benefit greatly from superior amplification.

Testing setup:


Nuforce uDac > EF-5 > HE-5
 
vs
 
uDac > Sennheiser HD 555 (foam modded, with thousands of hours of burn in)
 
 
Out of the box, HE-5s sound abysmal compared to my HD555s through uDac. That came as a bit of a surprise to me, as I expected them to sound better even without burn in. I appreciated a drastic improvement after a few hundred hours of white noise, pink noise, and sine wave sweeps. However, since I was listening throughout the entire period intermittently, it might just be that I was getting more accustomed to the sound of an orthodynamic headphone, or a combination thereof.
 
 
When these headphones work properly, they seem to be heavenly. Incredibly natural presentation and fidelity is the main strength of these phones. However, sadly, these phones are riddled with weaknesses. I've barely had time to explore the strengths and nature of these headphones thanks to debilitating build quality courtesy of Head Direct.
 
 
Out of the very simple box (which contained no manual or instructions, just the headphones & a few replacement cable connects screws), the headphones were damaged. The top left wooden headscrew had chips missing, and the bottom right hole for the cable connector had a hairline crack running through the center. Sadly, I did not think much of it until after my 30 day period for a refund had run out and I had read posts on the forums detailing some customers who had to replace their HE-5s a multitude of times in the course of under a year due to wood cracking alone. Living in Canada means that sending these in for repair would cost just under $100 and at least two weeks of downtime, (or $50 and 3 months of downtime). For now, it appears to be cosmetic. While I wouldn't return an HE-5 merely for cosmetic reasons, I am definitely worried about the stability of my phones as a whole because of the severity of wood cracking for most customers. I'm also reluctant to spend $100 in the process because I suspect that the wood cracking could be caused or aggravated in the process of transit to and fro the long distance.
 

So far however, I have not used my HE-5 for a few weeks for more than 20 minutes (read on to see why). I've coddled it and babied it, and the wood cracking seems to be benign for now. However, if it ever got beyond the point of cosmetic and actually affected performance, I'd want a refund, regardless of if the date is over. That sort of build quality on high-fidelity equipment is utterly unacceptable.
 
 
Just yesterday I went to meet another HeadFier to attempt to help him verify if his HE-5 had strange treble. We concluded that his had a wider and more pleasing soundstage, while mine had a more amiable treble. The colouration of the wood between the two was also distinctly different (his was darker, as opposed to my lighter wood), and his had less if any wood cracking (at least none that he noticed in his short period of ownership - buying it from another HeadFier). His model was from December 2009, mine in March 18th, 2010. The difference between the two is rather unreassuring to say the least. Head Direct has serious quality control issues to let this be. It is possible there were two different types of wood were used, quantifying the differences we heard.
 
 
Another unfortunate aspect was my EF-5 amplifier. The power supply was faulty out of the box (I set it at 18V / 115V before I plugged it in). My EF-5 would die out randomly when the dial was past 40-50% (more frequently the higher it went) requiring me to restart the system. 3 weeks after arrival, it finally died completely, forcing me to return it for repairs. I am currently unable to use my HE-5s which I had only just finished burning in and have barely been able to see the true sound signature of them.
 
 
From what I recall, about 2 weeks after receiving the combo (when the HE-5 was about done burning in), I really, really loved the sound. However, yesterday, auditioning and A/Bing my HE-5 with the other HeadFier's EF-5 + his Dac and my uDac, I was really quite unimpressed. Maybe it was the less than stellar conditions of the room (though it was relatively quiet, HE-5s provide 0 isolation and leak like hell). He also agreed that my HD 555s sounded about as good, if not better at some parts than his HE-5, which was sparkly in treble that my HD 555s did just fine. Admittedly, the HD 555s were foam modded and had thousands of hours of burn in, but the HE-5 should be in a completely different league.
 
 
Recently, I've been just listening to my HD 555s and I've preferred that to what I heard at the audition yesterday with the HE-5s. The HD 555s were put in the same situation, and I think they did just fine.
 
 
When I get my EF-5s, hopefully I can get back to giving my HE-5s some love that it deserves. I think that I've been criticizing it too harshly and not seeing its positives. It may work better with a fully working EF-5 and I'll also be trying the Musical Fidelity V-Dac to go with it. The star ratings could improve significantly if the wood cracking stays as cosmetic for the years to come, and the sound opens up even more as I use my HE-5s more, and I grow more accustomed something that doesn't sound like my regular dynamics. Unfortunately, I don't know if I can properly deal with side clamping pressure and overall lack of comfort - it hasn't really improved since I first bought it. Only time will tell - probably 2 more months before I receive the repaired EF-5 for more testing. If I only see more debacles come out as a result, I'll be definitely in the market for a different setup, perhaps HD 650s, Lambda Nova Signatures, JHxx Pros, etc.
 
 
As a final note, I almost must say that Head Direct & Mr. Fang Bian (Fang1 Bian4, Mr. Convenient in Chinese) has been very inconsistent in their dealings with me. They ignore about half of my PMs & emails. They simply redirect me to emailing them on their MSN contact (why do they have it, then?) which goes back to the ignore cycle. However, dealing with them by phone seems to be fine. Others have had much better experiences dealing with them, and this seems to be a drastic outlier, but hey, it happens, right?
 

Summary
 

Sound Signature - needs more testing
 
Build Quality - Terrible - wood cracking, alternating quality between different headphones of the same model. In comparison to HD 555s, I've used them as a portable and at home for thousands of hours, put them through hell, literally smashed them dozens of times, and exposed them to hundreds of hours of moderate to excessive rain, and even bent the gold plated connector. They still work as good as new. Oh, and it also blocked a pile of bird excess from hitting my head
 
Comfort - subpar, too much side clamping force (not like a vise but definitely gets very annoying very quickly. It is pretty much impossible for me to listen to a full album on these headphones, thank god for shuffle playlist), top (headband) isn't cushioned, just overall 'meh'. HD 555s are vastly superior in this regard.
 
Isolation - none at all, blocks out nothing, lets anything in. Very similar to speakers in this regard. Definitely bleeds more than HD 555s, and blocks less (even though they are both open circumaurals).
 
Extra Features - very bland packaging and manuals and stuff, presumably to save money (no manual or any text at all, some replacement screws [for the cable] are all that is included). Not that it is hard to figure out what to do, but it is a nice touch, and the Senns win again.
 
I really sound like a sullen old man suffering from buyer's remorse of the FOTM, don't I?


Edit: I may have to adjust the audio quality ratings - I really may have tricked my mind to adjust to the sound rather than objectively improved the overall SQ with burn in. I would agree with this post:
 
 
Quote:

EddieE said:

I'm aware that it can take 24 hours or so for the moving parts in a phone to calm down, sometimes a little longer. It's the hundreds of hours claim which lead to people waiting till a month of listening to judge their phones/amp etc.
 
It's a very convenient claim for manufacturers isn't it? That's about the length of time it takes
the human mind to get used to something it doesn't like at first and come to see it as normal.

Click to expand...

 
I also must say my comfort and design ratings are very subjective - as stated before, I seem to have received an outlier product that is especially abhorrent. However, do not expect the 'average' HE-5 to be much better. I've seen other HE-5s without wood cracking (the one I A/B'd didn't seem to have any) and the owner personally didn't have comfort issues to the point that I did. Just food for thought.