A great game.
When I first got this game, I beat singleplay mode in... oh, two days. Pretty easy, AI was not unfair and I never felt the game was onesided. I loved it.
Customization was great as well. You can make your own levels, change your worms color, voice, and victory dance, AND your team flag. I love games with huge customization, so this was a definite plus.
There are many minigames, such as the labratory games, as well.
But if your looking for a really fun time in Worms Open Warfare 2, then you have to do multiplayer. Multiplayer with one DS is fun, but not everyone sees the screen all the time. Multiplayer via ds download is great, but occasionally I experienced glitches where the game would freeze up and lock up the whole thing.
Nothing is as fun as WiFi battles though. I still go back and play WiFi and never get bored of it. It's one of the very few Nintendo games where you don't need that annoying "Friend code" to play online. This is probably the best point in Worms Open warfare 2.
Problems are minor, but I was surprised at the number of glitches I encountered when playing. Sometimes when I'm creating a level some buttons will turn to pixel blobs and ather strange things will happen, like lines on the screen. Sometimes the game will lock up and you have to turn off your DS and turn it back on. This gets particularly annoying in WiFi matches because it makes you look like a quitter. (Some guy in taiwan's all like "heeeeeey.... He just a big quittah!!! Now I hafta turn offa my DS and staht it uppagain!") Sometimes, unsettling noises come from the cartridge when these glitches occur, like loud "pop" noises.
Of course there's always the possibility that my game cartridge is screwy. hmmm.......
Overall, if you have a DS, get this game for your collection. It's replay value is huge and is actaully better than going through it the first time. This is a great game.