Best multiplayer ever.
I've played this type of game on several occasions before. My friend used to have Worms: Armageddon or something like that and we had a good time with that but maybe only played a couple times together. It was enough of a positive experience to convince me to try the DS game.
Anyway, the graphics are colorful, well animated, and fun. Nothing wrong with the appearance here. The environments are carefully drawn and each area has its own hazard which makes it interesting and adds a large element of luck (but luck doesn't always trump cold, hard skill). This luck factor keeps things fun, light-hearted, and difficult to predict.
The controls are basic, and you have a decent assortment of weaponry to choose from to blast your enemy annelids into oblivion. The game is relatively well balanced in that basically every weapon has its practical uses and of course its situations in which it is not the best choice. Still the strategy in this game is simple enough to make a pro out of anyone, yet complex enough to really open the door for those who can really aim carefully and calculate strategically to master the game in a way some others maybe could not easily.
There is a handful of things to do in single player mode in order for you to earn money to unlock extra weapons, skin colors, voices, level themes, and some other stuff I'm just not quite sure about. It's enough to entertain you, actually, which is surprising. You'd expect that a game this geared toward multiplayer would have a weak single player path, but it's really pretty entertaining and varied (as varied as this sort of game can be).
But, like you might imagine, the multiplayer is where this game shines. You can even play with a single cart. I'm not sure what the difference is; I imagine it just has to do with the other person being able to select their own custom team if they have their own cart, rather than having to select one of the pre-made teams. Not that that really makes any difference.
Multiplayer is tons of fun. This is one of the last games you can have a ball with with only two people playing. In fact, more than two and it probably gets tedious and you'd probably start to feel a little antsy waiting for your turn.
So I have to give this game a 10 because there's really nothing wrong with it. It's got a solid amount of content and anything added would be too much, anything subtracted would be not enough. The single player is good, the multiplayer is great, the graphics and sound are nice, and all-in-all, the game's just.. good... so enjoy! If you bump into this sucker at Target or Best Buy, consider picking up a couple copies; one for you, and one for your friend.