It's very frustrating that completing the last level doesn't give a skill point to max out skills. There are certain parts of the last level that seem nigh on impossible, and the extra skill point would make a difference.
The 4th tower down on the left hand side is ridiculously overpowered, no need for any other types as soon as you've got a decent amount of starting money.
Buggy, which is unusual for an Armour game. After pausing twice in the first level, refused to send any more enemies. Then after restrating got 99% complete as it said I was victorious before seeing the final boss.
To those moaning about no achievements... There was plenty of debate at release time, turns out that the collective couldn't get the API right so that Kong could implement achievements! They tried harder on TSG: Missions, which is why that one has achievements - and is a harder and more rounded game, this is just a warm up!!
I'm glad a lot of the comments share my frustration. The second I realised I would have to juggle to beat a level I walked away, just can't stand it, too intense.