Terrible online problems hurt what could have been XBL Arcade's crown jewel.
Quarter match mode is fantastic when it works. I do wish you could have more than 4 people in a room, but at least this way you get to play more often. Playing together with 4 friends in round-robin style matchups is a lot of fun.
No "New Challengers" to be found. This one is more a matter of opinion, but a lot of people feel the game lost some of its balance and appeal when Cammy, Dee Jay, T. Hawk, and Fei Long were introduced. I don't really disagree.
Difficulty. Again, this is a love it or hate it subject, but I like it. The SNES version was too easy, which is why a lot of people now are complaining the XBL Arcade version is too difficult. It's not too difficult, it's just a direct translation of the arcade version, which is meant to kick your butt so you have to put more coins in. Cranking it down to level 2 or 1 makes it easier for those who can't handle it.
360's controller. Personally I've gotten used to the d-pad, but I'm in the vast minority. The left thumbstick isn't bad, but for those of us hooked on using a Saturn-style d-pad for fighters, this doesn't come close.
Online. Terrible, terrible, terrible. Dropped connections left and right. Timeouts. Lag. I know the lag isn't always the fault of the game itself, but if the other two things were fixed it would make the lag a lot more tolerable. This game needs a patch in the worst way.
Not a bad purchase, but it would be a lot more palatable if MS charged $5 like the should have, instead of 10 bucks. For about $5 more you could pick up SF Anniversary Collection on XBox and get this game (with the New Challengers) AND Street Fighter 3 both with online play (and the ability to use a decent arcade stick - no, the DOA4 controller for 360 isn't "good").