As other reviewers have pointed out, this is a direct port of the Wii version of the game, the one that got higher scores than the Xbox and PS3 versions. Therefore having a Wii game on a handheld has a high coolness factor. The game experience is simple/dumb smashing and bashing with little strategy required. There is a nice set of different moves that can be unlocked, but the basic moves work in most cases as well or even better than the fancy moves you can unlock by spending the in game earned tokens. The special moves are cool, but pulling them off requires a high amount of dexterity in the limited space available on the 3DS. The results of having to press certain shoulder + face bottom combos is cramp.
Visually the game doesn't improve on the Wii version, in fact it looks slightly better because the screen is smaller, but the resolution obviously takes a hit. The 3D helps a bit, but there isn't a lot of it. In some areas it is hardly noticeable and in some of the pre-scripted game sequences it looks really well. The cut scenes, artwork, menus and the cartoon dissapointingly don't have any 3D at all, which is a bit of a let down and cheap. The advantage of the 3 D not being pronounced, is that you can crank it all the way up without issues, except during some boss battle sequences and in small (cramped) spaces where there is a fair amount of clipping and headache inducing focussing issues.
The sounds are fine, especially with headphones. The two main characters are voiced by the actors that also were in the movie, so that is good.
There is a fair bit of content, moves and abilities to unlock, but even then it isn't a long game and also not a very hard game. Other reviewers have said that it can be finished in 4 hours. That is probably true if you don't care for the unlockables (moves, upgrades and artwork). Trying to collect everything will take considerably longer, even though even at hard mode the game doesn't get difficult until the final stages. It is probably possible to get everything unlocked within 8-10 hours, which is really short as there is no multi-player and also no brawl type of game play. wireless play is mentioned in the manual, but that doesn't give any details on how to actually select it. The manual clearly was a rush job, with only one page of control information and that's it! After beating the game the ragnarok difficulty is unlocked, but finishing the game at that difficulty is just for bragging rights (if you are into that sort of thing). There is a bunch of cartoon episodes that are gradually unlocked while playing the game. The same as for the Wii version. It would have been extremely nice if these were given the 3D treatment, but they are just normal 2D instead. Still that's a nice addition.
The touch screen is hardly used except for displaying what is enabled and for unleashing certain special powers. That sounds okay, except that some of the buttons are tiny and that all other menus are strictly no touching.
This is a lazy port, if you own the Wii version, don't bother it is the same, but less easy to play. The controls are a bit of a let down, not much thought was spared on how to make use of some of the strength of the 3DS. Essentially it is a cheap cash-in. Still it is very satisfying and fun to play even though it is very easy and tempting to resort to button mashing. Sega obviously are aware that this game is months too late and have decided to sell it for 30 USD, look a bit harder and wait perhaps a bit longer and you can probably pick it up for 20. That is about as much as it is worth, for a couple of hours mindless brawling.