Rock solid TD
Very polished. Great graphics, great audio, great (if utterly unoriginal, but hey: I love TDs) gameplay.
I dinged you on the lack of variety.
**In weaponry: PB AOE, slow, poison, buffs, etc. Just some towers with short range/high DPS, and some with much longer range would make things a bit more interesting. You could accomplish that with tweaks to the existing stats.
**In enemies: speed, resistance to various weapon types/effects.
Also, replayability. I know I could create a new save to go back and try previous levels again, but why do I HAVE to?