Very fun and good-looking game, but too easy...
The game is a simple defense one, where zombies attack your house, and you have to fend them off using various types of towers (plants). There are so many plants to pick from, and each one very creative and interesting. The zombies also come in different forms, which mixes the game up a bit. There are also a couple different modes, such as Bowling (is that what its called?), where you simply lob coconuts at the oncoming zombies - a nice addition to the otherwise same-ish gamemode.
On the downside, the gameplay tends to get a bit boring, laying down towers and killing zombies. A different tower only arrives after you complete a stage - and these stages can become a bit boring.
Also, the game as a whole is WAY TOO EASY. Its almost impossible to lose! This makes it a bit boring and repetitive, as there is not much strategy required.
Plants vs. Zombies is a game you have to at least play, if not own. Its a classic defense game, one of the best on XBLA.