I have it and I do enjoy it. The grahpics believe me are better. The game play is quite similar though with some additions. Including three new mounts for the brown, green, and red minions. You can also use catapults and stuff. The tower customization has been expanded and you can now have 3 mistress at the same time! More the merrier? I'd say so far it was worth my 40 bucks.
However warning with those who have an 8800 gt. For some reason after about an hour of playing my gfx's gpu rockets to about 100 Celcius! And then of course my pc restarts to save its sorry butt. This might not be the games fault as the card is supposed to increase the power of the fan the hotter it gets, but it doesn't seem to be doing that. So, I have to go into nTune and set the damn thing to about 80% fan power just to keep it around 70 C so it wont take a hot steaming dump onto my motherboard.