Immersive and loads of fun, you won't want to put this one down!
The combat system is unlike anything I've ever seen before, but once you get the hang of it, it quickly becomes an immersive and fun to play system. I never thought the touch stylus stuff worked especially well here, so I'd certainly advise using the face buttons instead. The AI is also challenging enough, but I'd almost certainly want to play against an actual human instead.
It can be difficult to describe the gameplay, so I would advise looking up some videos on youtube, however, the move limit is the perfect amount to force quick strategy without going so far as to cause massive frustration. It makes even random encounters fun to battle and there's always the option of just jumping into an AI battle against a random or chosen opponent. Each character also has a special ability, which vary widely in usefulness, but still add another dimension of strategy, as do artifacts which grant the user different benefits and abilities. Luck does play a small factor, but not as heavily as it does in many other puzzles games (I'm looking at you, Puzzle Quest, and your extreme rubber-band AI) and luck is almost never poor enough to ensure you'll lose a match (you'll sure want some on some of the boss fights though). In the end, good strategy is the way to win and it's what makes it so worth playing.
Might & Magic: Clash of Heroes dominated my DS slot for months after I picked it up and it was difficult to make it leave until I'd at least beaten the campaign. Even now, I'm always tempted to put it back in and get into an instant battle. It's a good match for the DS, but it seems like the metagame is happening over on the PS3 and 360, which is enough to tempt me to buy the game all over again! No matter which version of this game you may be tempted to buy, buy at least one because it's some of the most fun puzzle/battles you'll ever have.