I paid $15 for those headphones, and I did not expect anything great. They aren't as comfortable as you would expect, but it does the job. The sound separation is poor for Sennheiser quality. I own a pair of HD 212 pros, which can be purchase for around $20 now, and I have to say that they are much better in every aspect.
 
I don't recommend HD 201s.

Not the best headphones. Sound is mediocre and is not much better than a decent pair of IEMs. 
 
Worth mentioning that they fell apart after a year of use. I am not over exaggerating. They fell apart.
 

Value: 10/10
For its price range, Sennheiser HD 212 Pro are one of the best buys out there. Nothing much to add here.
 
Audio Quality: 9/10
Great bass, mids and highs are good enough. Sounds like the $300 Beats Studio.
 
Design: 8/10
Not the best design. The look isn't great, but considering its price, I would not complain much.
 
Comfort: 9/10
Main asset is that they are very light. Feels great wearing them.
 
Overall: 9/10
Great buy and great bang for buck.

Background
 
Up to date I have owned a couple of headphones, including a useless Icemat Siberia, a few Sennheiser IEMs, some mediocre apple products, a pair of bose that I borrowed for a while and finally the Sennheiser HD212pro that I have been using for the past couple years. 
 
Due to a limited budget, I have decided to stay with my HD212pros since 2009. They were comfortable, light and provided good sound isolation. The base was great for the money I paid, which was a really sweet bonus. Simply superb for studying/work. My interest in headphones was rekindled when two of my friends bought themselves headphones that I have never heard of before: Beats Studio and Beats Solo by Dr. Dre. When I was told that they paid $300 and $200 respectively for those monster products, I felt compelled to try them. My impressions? Not much better than my 3 years old HD212pro, yet ten times more expensive.
 
I have decided to buy the HD595 primary due to its great cost-to-price ratio. The HP, LOD and amp was just enough for my budget. The reviews on head-fi were favorable enough to convinced me that this will be a good buy. Today, I can boldly say that those are my first real headphones. I love them. 
 
Review
 
audio quality: 9/10
Lacking the bass that could have made this headphones godly. However, great mids and highs make up for this. I listen to a lot of rock music, hence I don't feel it as much yet hiphop or eletronic music fans may feel somewhat disappointed. Also, having a good amplifier does help bring the best out of HD595 but it is not necessary - they are great even without it.
 
design: 8/10 
everything is great except for the jack and general connectivity. It it not as annoying as just a small detail. Can always buy a different converter.
 
comfort: 9/10
feels great, very, very comfortable and fits perfectly to my head. Haven't experienced sweating around my ears like in the case with some headphones. A little heavier than what I am used to, but it is not a major issue.
 
value: 8.5/10
the fairly low price and great quality make those headphones a valuable purchase. Especially for people who listen to a lot of vocal/rock. A very weak bass makes those headphones unsuitable for hiphop or electronic music.
 
overall: 8.5/10
I do realize that there are headphones of better quality that do not leak sound and are stronger in bass. However, when comparing the price of a little bit above $100 to $1500 for HD 800s, I consider HD595 a great bang for bucks. This makes them a great overall mid price range headphones.