I've played it in the past -- it is quite addictive when you first start out but I find it gets very boring after you've beaten the game several times.
A year ago I never played it to completion in the first version; I think playing Plants Vs Zombie interesting and funny zombies with character that is mixed.
Coincidentally was playing this yesterday in a hotel room when the internet connection went down. Not played it for ages. Even after you beat it a few times you can still play the puzzle games like the neverending ones where you are the zombies. Good game.
Personally, I love to play scary games more. Zombies games are more horrible and suspenseful in every tasks of each and every stages and next level.