Yes, rollback did wonders for SF4, i tried myself and got pretty good results with my crappy internet, and was even surprised that i was able to hit 1 frame links after a quick adjustment, it still felt different from playing offline. Still the result of balance in SF4 its not based around online, from what i've seen, its mostly from a lot of data gathered from tournament results and players performance on those tournaments.
An approach NRS should do more often rather than listen to players posting "Scorpion teleport is broken!" after 3 days of online play.