Pros: Supreme comfort, supreme long-term listening, works with most music, easily amped by common sources
Cons: A little too "repressed" for rock n' roll, atrocious 1/4 to 1/8 adapter
I've owned these Senns for over 3 years, and don't plan on getting rid of them either, even having bought an audibly superior set of phones from a competitor. Hopefully that says a lot - these are too good to just abandon, but not quite good enough to have satisfied me til death do us part. I have discovered that they fare even better with a quality Amp/DAC solution, which was a nice surprise. With better equipment, they certainly hold their own against my HE-400s, and call the value of the extra-costs of buying the HE-400s into question. But, without question, their performance has some limits which coaxed me to finally move on.
I find these phones to be extremely enjoyable for low-moderate volume listening and long wearing periods. They are very comfortable, light, and the 1-sided cord doesn't get in the way often.
The design is tasteful. The headband and velour pads are soft, supportive, and overall a sense of quality is conveyed. The cups adjust to your head 'automatically', though I have noticed that positioning has an effect on the overall sound - it is easy to fall in and out of the 'sweet spot'. Stock cord includes a 1/4 inch plug, which should have been a 1/8 since I've never in my life used them with something that had such a jack. The adapter sucks - put it on and you have a stiff 4 inch long plug hanging precariously off your laptop, phone, Mp3 player, or computer. I was too cheap to replace this, and luckily no accidents so far. I never cared for the color scheme, which is somewhat too drab for me. But these are light, comfortable, and have proved durable. Minimal signs of wear in the years I've had them, and absolutely no issues.
Sound quality is superb across a wide-range of music formats, with a very detailed sound, fairly textured bass, good vocals, and a slightly forward (but polite) treble response. I think the sound is best at low-mid levels, as they can seem a little too forward and "fall apart" a bit at high volumes. They otherwise have a nice punchy mid bass with most music, and a slightly aggressive presentation which is more spacious than most other phones I've tried. They are well balanced, and the sound is generally never fatiguing if volume levels are kept in check. They are excellent for very-long listening sessions. I can't recommend them for rock and metal, as they are a little too laid-back to make those their best formats. I can't recommend them for "bass heads", as these cans are geared more toward those who appreciate a balanced presentation.
These are an excellent choice for those who want to experience a high end sound at a reasonable price, and who want to avoid investing in expensive audio equipment to enjoy them. As a result of owning these, I would not hesitate to purchase other higher-end Sennheiser product. I would simply be cautious about choosing among them, as I like headphones that presents modern rock, pop, and metal in a more transparent and energized fashion, and Sennheiser seems to err on 'comfort' over exitement.