The best 10 dollars spent in awhile
The main adventure is perfect length and starts to gets progressively hilarious with the first encounter with Crazy Dave or the Bobsled Zombies. The levels are split into stages to add more variety to gameplay and different plants to chose from. The night levels add more difficulty since the sunflowers can't produce as much sunlight to produce plants quicker, the backyard with the pool adds a change of strategy since now you are forced to defend the pool by placing lily pads in the water first in some cases.
During the adventure, mini-games, puzzle games and survival is unlocked to add much more replay value after the adventure campaign is over but you'll want to play it again to get more money to unlock more plant upgrades and unlock zen garden plants where you can care for plants and earn more money and unlock even more.
Plants vs. Zombies does it right on many levels, very high replay value, variety of ways to play and a variety of modes to play to keep anyone entertained for a long time. The only downside I see is how easy the adventure is from the start and it's not until the later levels that really get challenging but a second play through of the campaign adds more difficulty that will have you testing your plant defense capabilities.