I got my chance to try it out yesterday at my friend's place. In fact, we ended up playing most of the afternoon.
I'm not going to get too technical, but the game is slowed down slightly and you can't really buffer inputs (at least not as easily). I'm not really into the critical finishes or the the armor breaking, though. I spent the whole time playing as Amy (my fave from the previous game) and thankfully she's not a whole lot different from SC3 Arcade Edition.
All in all, I give it an 8. It's as fun as the previous iterations with the addition of playing online (360 is less laggy than PS3, I hear). It also has create a character in it which gives it quite a bit of replay ability (plus the unlockables from Tower mode). I'd say get it