I just got my X700s. Popped them in and listened to some of the songs I know best. I'm coming from Grado SR-60s and I am most interested in how these sound compared to the Grados, as they are supposed to be a replacement. Some notes...
1) wow, these sound a lot better than I expected them to. I was really expecting some crappy sound (I've been let down by budget praise re: Sennheiser HD-201s, JVC Marshmallows, AKG K501s, DT880s, Sennheiser HD580s etc etc). These really do blow my mind, considering I got these for $34.
2) From my now faint-and-vague memory of AD700s, these sound very similar. Very well balanced across the spectrum, a lighter sound than Grados, but still enjoyable.
3) Detail is fair - the only thing it's missing on the SR60s is the Grado punch and attack. Cymbals sound very good, but are far away. Some of the mids are being smeared, though, and the bass is a little sluggish... hopefully after some burn-in these problems will be rectified.
4) Soundstage is excellent. Very immersive headphones; also similar to AD700 soundstage. EDIT: okay, just listened to some Angra. Coming from Grados, the sound stage is HUUUUGEEEEEEEEEE!@@@@!!!!@$!@@%!%%!%!9000000!!! It might just be because I've never really had much time with circumaural headphones, but man, these things make my head spin.
5) These are pretty comfortable initially, but after about 20 minutes I can tell how these will get fatiguing. The pads just aren't very comfortable. Hopefully this will also get better as I put more hours on them...
6) They also don't get rid of my headband hair problem

7) Tried them out for gaming for a little bit and I think I was most disappointed here. Since I played with my Grados for many years, I was used to the drivers being directly on my ears - because of this, I could use the
CS:Source sound directional cues amazingly well. I put the JVCs on and... well... I can't really tell where exactly sounds are coming from anymore. It also seems that there's some sort of strange thing where everything sounds like it's coming from more "behind me" than in front or by my side. I'm not sure if this is due to the circumauralness, the driver orientation, or the fact that the earpads are thicker in the back to accomodate for head shape.
But for $34, these are ABSOLUTELY AMAZING. I don't think you can go wrong with these things...
EDIT: for reference, I listened to some Dream Theater and Symphony X while making these impressions. I'm listening to Backstreet Boys - The One (for old-times sake) and I'm not particularly enjoying the way it handles the tsh-tsh-tsh... more to come in a bit. I'll run these through all my genres and see what else is up.