Summary: I had the original Street Fighter IV that came out. Then all of these new upgrades/versions came in the following years. I was tempted but I'm glad I waited until the end to purchase this most recent version. I'd suggest getting this if you haven't bought all of the previous versions (unless you really need to have this). For me, it was definitely worth it. As for the game, it's just classic Street Fighter.
Summary: Compete seriously or play casually! Ultra Street Fighter 4 is still the top played game at EVO. I personally like having a disk so I can play with friends around town if they don't have a copy. But if you already own any of the Street Fighter 4's, you can simply download the upgrade for about $15. Just a heads up... EVO and nearly all USF4 tournaments across America play ONLY on Xbox 360.
Summary: Excellent version of one of the best fighting games ever. This is the definitively version that includes fives new characters and is highly recommended for anyone who doesn't buy the game before.