The online totally works. Really, that might be the only piece of info you need to see. While it'll act a little funky if you're playing internationally or against people with awful connections, it feels fine to me. I'd guess that if you were counting frames, though, you'd probably notice some differences.
Maybe it's just a time of day thing, but the people I was playing last night on the PS3 version were wiping me out. Totally better than me. Now that I'm playing the 360 version, though, I'm running through most players without too much trouble. I think I've lost one match so far, maybe two. Also, I managed to get three perfect rounds in a row against one guy. Another guy's whole strategy was to pick Fei Long and just hit roundhouse over and over again. Duhhhhh.
I ran into a bug on the 360 version where the music just stopped playing during fights. Still works at the menu, but I guess I'll need to quit and restart it to get the music back.
The game lets you revert to original character graphics, original music, and original gameplay, if you want. There's also a pretty heavy menu of switches that let you turn on specific elements of the remixed gameplay, like if you'll be able to "store Honda's command throw" or not.
I thought the new artwork would bother me way more than it does. The "new art, old frames" look still seems a bit choppy, but that's by design, and it's not a big deal. Speaking of which, most of the new art is A-OK. I think the only thing I don't like is Blanka's face. Maybe that's the point.
Oh, and they totally got rid of the stupid-ass announcer that popped up in Super, and changed some of the voices, too. Guile doesn't sound totally horrible when shouting "sonic boom." They just reverted it back to the pre-Super voice. This, alone, makes the entire "remix" worthwhile.
Pretty smart changes, all told. At least that's how they feel so far. More soon.