A classic resurrected via Xbox LIVE adding a whole new element of awesomeness.
However, those are the only negative aspects I can think of regarding the game. The one problem I have with most fighters is that I can never find anybody to play with, and UMK3 supports full XBL features. A great head to head mode with a simple yet effective "tournament" system of four players per host, in which I have very rarely experienced any lag, and with full voice chat and leaderboards available if you're in to that sort of thing. The multiplayer features completely change the game from fond memories to great current title. I still find myself picking up this game, so to speak, and learning the moves, combos and fatalities of new characters.
In my opinion, Ultimate Mortal Kombat 3 is the highlight of the entire Mortal Kombat franchise. It introduced a combo system that is generally simple yet effective, and the game mechanics offer all sorts of deeper play if you want to REALLY get into it, yet it's easy for someone to pick up and play well if they only want to spend a bit of time learning the moves. And the characters in this version of the game are excellent. This is before Mortal Kombat got all crazy with the addition of too many stupid characters.
I think my biggest gripe with this game is that Johnny Cage is not in it. He was my absolutele favourite character in MK II.
All in all, this is an excellent revival of a classic that is easily worth the measly Microsoft points, and if you enjoyed the original it will definately be an XBLA game that you will come back to regularly, especially if you have a few good competitive friends.