Great classic but incredibly buggy at the moment. Hopefully a patch will fix the glaring errors and make it perfect.
The main difference between this version and the others is the online capability. Players are now able to battle competition at any time via player-created lobbies or ranked matches.
The infamous jazzy music from the original is retained but gamers can now use their own music on their systems. It's a great way to hype yourself up for your ranked matches or battle it out with your friends.
You can now play in widescreen mode which will get rid of all the empty black borders. You also have the option in playing in the original aspect ratio of 4:3. Character sprites also have different filters - nothing revolutionary like Super Street Fighter 2: HDR, but it does it make it much prettier.
Some problems arise with online play, however. Picking any option other than quick match (at the moment) often results in your Playstation 3 locking up and requiring a hard reset. This is the first time I've ever had to do that.
If you're a casual MvC2 player, that's probably where your problems end. For the competitive community...
...the game is a huge disappointment. The bug list continues to grow day by day whether it is has to do with unblockable AHVBs, different animations for Magneto's ROM/Cyke's infinite which change the timing, and a plethora of other grievances. At the moment, the PS3/XBOX360 version of MvC2 is in NO WAY tournament viable. If Capcom does not fix these problems, MvC2 will probably be expunged from Evolution.
Overall, this game is still a must have. If you're playing it casually, there will probably be no problems other than lag and the realization that top tier completely dominates. If you're playing it competitively, however, you'll find at the moment you're probably safer practicing and playing with your friends on DC.