Very fun!
Just finished the game with 36 lives remaining, using 10 dart towers, 4 tack towers, 2 bomb towers, and 3 super monkeys (although the last super monkey was purchased near the end of round 49.) You should have a round 51; Black and white balloons coming in an unending stream just to see how good your defense is, with no buying allowed. All in all, a very fun game! I know I've spent at least 2 hours playing this game, probably the most I've ever played any NG game.