This is one of those games thats just pure simple fun. Its lack of depth, while in many ways a downside, enables you to play the game for long periods of time without getting bored or tired.
I was hesitant at first to play this game, since I'm such a fan of the PC Baldur's Gate series, but this game impressed me as a good action RPG in its own right. Like in the original Diablo, you pick one of three playable characters, and run through dungeons are caves killing anything that moves. The boss battles and level-ups come quickly and frequently, the game never gets too hard (unless you want it to), and the setting changes often enough to keep things interesting.
The story in Dark Alliance is kind of shallow and muddled at times (something about a Dark Alliance of monsters preparing to invade the city), but this isn't a game you play for story. Story is sacrificed for lots of action and smooth multiplayer, and in those departments Dark Alliance is a success.
Dark Alliance doesn't strike me as a great game (not in the Diablo II sense of the term), but it is a good action RPG. Its fast-paced, graphically beautiful, and, above all, fun. It probably won't shoot to the top of your list of favorites, but you'll have a crapload of fun playing it, and thats what matters.