I like this game so far. The tilty controls feel gimmicky at times, though, such as rolling the Luigi ball (it's not too bad, though). The giant fights are really fun though, but I feel that the touch screen gets a bit unresponsive when Luigi tries to dodge the attacks. Also, the game is a bit tutorial heavy, but I don't mind that, especially since this is my first full playthrough of a Mario & Luigi game, even if I played some of it before.
The good things about it is first, the graphics. Wow, after all these years of New Super Mario Bros., Mario & Luigi feel fresh and superb. Also, we get original characters, unlike the NSMB muck-up that is Sticker Star. Bowser also retains his personality.
Plus, you get to control Mario more. The music is good, too. What I didn't like is that Mario and Luigi don't yell at the top of their lungs when the battles start, and I wish they can make some noises in battle to make it more lively. This game, still, retains the spirit of the previous Mario & Luigi games, and I like it.