I just got mine from Play-Asia about a week ago, and have played it a bit, though not exhaustively.
Overall, it's much improved from the DC port - the build is based on the arcade version, apparently, and as a result, corrects for combos and certain hits only possible in that version, as opposed to the DC one.
I'm not much of a great SF series player, but I've been enjoying it a ton. The biggest changes to my eye have been in the graphics - it feels sharper in terms of resolution than the DC version, with better definition, and perfect screen size, and surprisingly, there are close to zero loading times. In fact, I was somewhat shocked at how minimal the loads are. Music is great, as it always was, but I don't recognize anything significantly different from the DC port - it could be just my imagination, but the defaut balance of music to sound effects seems improved.
As far as gameplay goes, it's the same game you know and love. Frankly it feels like a perfect port in every way. The DC rev was already great, and this just added little touches of refinement. I'm sure others will have more in-depth analyses of the mechanics, but overall I'd say that this is in every way an improvement on the DC version, and a great port.