The survivor mode needs a new algorithm. I've been sitting on level 31 for over 10 minutes just killing creeps. Looks like the level will last at least another 20 minutes (already $4M cash). The total kill count on the defense core is also broken- it got over 100k can just counts from 0-1000 with a K after it over and over very quickly.
Too easy- the enemies give back too much health meaning that you can be rather reckless, but once they die you go back to 100% health. Load up on spread guns and nothing can stand in your way.
Really needs a lot of work. Did anyone else notice that archers are by far the best $$/power ratio? All you need to win are mass archers until you get to dragons, then put out a couple dragons each lvl and you win (last level you need 3). This needs tremendous rebalancing.