1up has new details on Street Fighter IV

http://www.1up.com/do/previewPage?pager.offset=0&cId=3165157

For those who don't wanna read the somewhat lengthy article in its entirety, here is a summary of important points:
-It will probably go multiplatform
-It's easy for anyone to pick up and play, but deep enough for more hardcore players
-The gameplay is strictly 2D, even though the background movements may say otherwise
-Some background objects are interactive (e.g. chickens may get roasted by fireballs)
-'Revenge Gauge': It is a lot like the typical 'power gauge', it fills up as you connect attacks and when it is full you can press hard punch and hard kick simultaneously to unleash an invincible attack.
-the Revenge bar also lets you pull 'Ultra combos' by performing a special signature attack (e.g. Shoryu Reppa) and pressing both medium and hard punch. Doing this activates a 3D cinematic (although the game is still 2D); it can also miss.
-Parrying is out.
-Online play is also available.
-New video tomorrow! First-ever gameplay footage.