The Ultras are really easy on a keyboard. Because you can bind a key to press all three of the punch or kick buttons at once in the options menu.
wait...dude this bound button you speak of is incorporated in the ps3 and x360 versions as well. the only difference is you dont need to set it in options as it comes default like that.
vellfire if you bought a fighting stick you'd not only enjoy sf4 but many other fighters that can be emulated.
at the moment im trying out first person tetris>>
http://firstpersontetris.com/?tetrisno idea why its called first person tetris, but just wait til you rotate a piece...
for some reason I find it easier than regular tetris.