Plays great, looks great, and has a lot of charm (even if some of the jokes are a little dated now).

The inclusion of boss battles on some stages was really great, since I didn't think a TD game like this could get me so tense, especially if you're going for that perfect score.

Having playable hero characters was really cool too, though I found that there was far too many of them. It would have been more optimal to have less, but you could develop them further.
The only gripe I had with the game was the last boss, since you had to cheese it due to the extremely frustrating tactics it uses.

Not much else to say, it's a legendary tower defense series at this point.