Summary: Best pair of headphones I have ever owned (sample size ~10ish). Audio quality excellent, directional mic is crisp and clear when in front of your mouth, picks up no audio at all when raised up. And most importantly, they are gloriously comfortable. I have worn them 16+ hours without any discomfort. If you are looking for a quality and willing to pay for it, look no further.
Summary: These are light and comfortable, they fold up for storage, and look good. The sound quality is excellent, and the microphone has good noise rejection. Easy to chat even in a noisy environment.
Summary: This is my 2nd pair of Sennheiser PC 350's. My first pair I used for years. The mic had gone out after about two years, but I still had it under warranty (just barely). I sent it in and they sent me a brand new pair. I used it for two or three years and the mic broke (must be a common problem). I use it now on my electric keyboard. All in all, one purchase got me two of these which lasted me 4-5 years. A few years later, here I am ordering this updated edition.
Summary: They're really comfortable. Velour pads are hot. These keep me cool and there's no irritation because there's no pressure on my ear. It all fits around. They are closed back which means you hear less background noise and they hear less whatever it is you're doing. The mic is pretty good too. I didn't even know they made these until my PC350s broke.The in-line mute/volume thing started to crackle. The PC350SE fixed that and other stuff.
Summary: When I bought this headset I already owned the Sennheiser PC 360 headset. This is essentially a closed-back version of the PC 360 as their design is very similar. The open-backed PC 360 offers slightly sound quality in my opinion, but at the expense of being able to hear everything around you clearly. My noisy roommates ended up making them less than optimal. The PC 350 SE does a great job at sealing out noise.