Yes, it's the DS version of a multiplatform game that has created mixed feelings, but I must admit I am surprised...
Yes, I love the MUA franchise, for I played the PSP and PS3 versions of both games, but since I traded my PSP, I had to get the game for the DS, which I was pretty suspicious of... .
The first impression was pretty good as the first level resembled a lot the PSP version with less impressive graphics. Combat system is almost identical but makes a good use of the touch screen, as fusion powers are easier to achieve. Levels are a bit shorter than in the PSP version, but it still maintains the same storyline. Some actions requires us to use the touch screen in very original matters (like disarming a bomb, which is not that obvious), but it has a certain watered-down feeling compared to the other versions. Nonetheless, it has a good selection of Marvel superheroes, and considering the DS as a short-trip portable console mixed with a training program mini-computer (unlike the PSP, more aimed at longer trips, being a smaller version of the PS2), it is definitely worth the cost, as you will be able to play your favourite superheroes in a compact, action-packed game. It is a fun game for adults and kids alike, as it's quite easy (but not too much, as boss battles are harder than in any other version) without being childish. In replacement of in-game movies present in the other versions of the game, there are animated slideshows reminding us of comic books. The effect is perfect and maintains our interest in the story as much as the aforementioned movies.
This is not the best DS game out there, but it certainly is one of the most fun and most surprising titles to have come out for Nintendo's portable console recently.