For mobile gaming on the droid this game is tops!
Pros: Its cheap, free version or a 3$ version, which I spent. It simply grows on you. The first round or two its actually a bit challenging to get through the whole level. The fun part is that you build reward points to upgrade your towers, which gives it that pseudo rpg feel. Furthermore you get achievements for different tasks which in turn increses your multiplier for rewards. A perfect formula to spend hours passing the time. Ive had no problems with the touch screen.
Cons: Well the graphics arent crisis 2 but theyre adequate. Overall they have a few different kinds of maps but I found myself just playing the one type. Similarly at the higher levels my maps are just a bunch of 2 or 3 types of towers. So a little more variety would have been nice. But not bad for a few bucks.
Overall just a great game for the droid. You can save and come back at any time and I found myself sitting on the couch playing this over my xbox some days.