Summary: These sound excellent and very accurate. If you want your head to shake from bass beats these aren't for you. IF you want to use them with a computer or iPod, you will need some type of amplification
Pros: Will built, accurate sound, very comfortable.
Cons: Too hard to store. Not portable at all, 1/4" plug. No adapter to 1/8".
Summary: I have had my HD700 for less than a week but I think I can make some reasonably accurate comments about it after about 25 hours of listening. I should point out that I my comments are influenced by my experience with a well-used Sennheiser HD600 with Cardas cable. I have used the HD700 with a PS Audio and a Musical Fidelity headphone amp. To say that I was underwhelmed with these cans when I first listened would be an understatement.
Pros: A broad, deep and well-defined soundstage. It has a better cable attachment system than the HD600 headphone. They look like they will last a long, long time. They fit on my head securely but I've been wearing them for 4-5 hours at a time without fatigue. They seem equally competent with pop, soundtrack and classical selections.
Summary: After building a very exotic valve headphone amp, with a Sophia Mesh Plate Rec. tube, I wanted to match this thermionic marvel with REAL quality phones. I have a pair of AT ATH700 Airs which I love and think excellent value for $160. I also have my "train" pair of Phiaton 400s with their closed back. The Phiatons are good but the ATs much better. I Googled for the "best headphones" the the answer came back "Sennheiser HD700s".
Pros: Un-coloured sound, feel solid and professional, removeable and replacable cord.
Cons: The cotton cord with a mind of its own, very open design lets a lot of sound out.
Summary: Just adding a quick summary based on my time with the prototype version of the HD700. In my opinion this is a very good headphone, yet I know it won't be perfect for everybody. But no headphone ever is! It basically takes the HD800 sound, reduces the treble energy to some degree, and possibly bumps up the bass impact a tad. Either that or it just seems that way due to the treble balance.
Pros: Exceedingly comfortable, easy to drive, many of the strengths of the HD800 at a lower price
Cons: The price will be an issue if it doesn't get discounted, highs can be bothersome, plastic construction may not feel like $1K headphones