If you have Super Street Fighter IV or Super Street Fighter IV: Arcade Edition, you can now purchase the upgrade to Ultra Street Fighter IV on Xbox Live and the PlayStation Network for $14.99. Unfortunately you'll have to wait until August 8th for physical retail copies as well as the full digital download version. The Steam versions of both the full game and the upgrade will also launch on August 8th.
Ultra Street Fighter IV brings in five new characters, six more environments, and more new content as well as some rebalanced gameplay. The only issue I have with it right now (and this was revealed a while back via Capcom) is that the new characters do not have their own challenges yet. For those who don't know, the individual challenges basically teach you the basics of a character's moves, their bread and butter combos, and some advance combos to help fine tune your skills with someone. The challenges for the new characters will be added down the road.