I picked this up after my daughter got hooked on it playing the XBLA version at a friend's house, and beat the story mode last night.
I enjoyed it for the most part. It did a good job of adding something new to the mix after almost every level. The art and sound design is delightful, and the interface nicely intuitive. The mini games at the end of each area did a nice job of breaking up the gameplay style.
One strategy seemed to work for almost every round in a wave. Once I figured out an arrangement, I found I could stick with that for most, if not all, rounds in that area. Most of the time the differences between rounds was very minor. Only one area gave me trouble (the roof) and that was mostly because I didn't like the design decision to force the back rows to be one of a handful of plants. It was an odd decision to slowly unlock this massive list of plants, and then have the final area be one where 2/3 of the gameplay space is limited to a couple types of plants added just for that area. It limited the gameplay and made the ending a bit boring.
Overall I definitely preferred Defense Grid on XBLA as a tower defense game. It had a better sense of build-up and less clutter to the deployable towers, and the levels were not nearly as repetitive. But this had its own set of charms and seems like a good casual/beginner tower game (though the end boss is a very large difficulty spike). And I'm going to go back and work through the puzzle mode, because the few I did last night were pretty fun.
Worth the $15 for the single player alone, IMO.
Edit: since this post I've played the fuck out of Zen Garden, mini-games, the puzzle mode, survival, grown an epic tree and done half the second campaign play through. So yeah. Lots to do here.
