A fun game, but I'd recommend increasing the difficulty level for the first playthrough. I didn't really see much challenge, and few people are going to play a second time through to see the enhanced difficulty.
This was a final, fun game in the series, but I was disappointed by the lack of difficulty. I breezed right through all 10 campaign missions on hard and didn't ever fail. The AI seems to be lacking compared to previous versions. I still had fun, but I missed the challenge from the first two versions!
I like the game, but Timestop becomes a huge exploit after a while. With Timestop at max, the enemy never has a chance even on Epic level. Get to the other tower, wait for first revenge wave, hit Timestop, hit Timestop again before the first runs out...tower destroyed...win :/