Great Game!
I really like this game. Yes it has a lot of similarities with DTD but the distinctions are notable. The money towers in particular are tons of fun... not only do you need to kill the enemies but where you kill them can provide HUGE boosts in income.
The electric floors are also a lot of fun. Do you build a narrow maze with more turns or leave room open to trap the floors. In combination with the money towers you can make some great combos out of this.