Street Fighter 4 is now available on Xbox Live as a Games on Demand direct download title for $29.99. Granted, most people have the game at this point but this could prove to be useful in certain situations where you have more consoles than you do copies of the game.
Now, I assume with this downloadable version of the game players will still have to unlock all the characters. If they offered this as a fully unlocked version of the game as a bonus, I think that would be a strong selling point. For instance, if they ever offer this on PSN, I don't have all the characters unlocked on my PS3 and might be willing to dish out an extra 30 dollars just to save myself the time of beating the game multiple times. This would come in handy at gatherings so I could have two stations set up with all the characters available.