Having gotten to actually play the demo and try my hand at each of the specialties, I can honestly say the gameplay is a big step up from TD. The controls are very much the same with few exceptions, but the responsiveness feels more fluid and less laggy.
The enemy AI is the stuff of dreams this time around! Very well balanced; I think back to how the AI was in Halo 3, where the enemies, too, would take different approaches to taking the player down. While there are limitations to that aspect, it was interesting to see how different enemy types attacked, compared to TD where they all basically had the same few strategies regardless of enemy type or rank.