Slow movement rate, little variety, no autofire, a penalty (larger target) for upgrading, support units do nothing against enemies coming from behind (unless you drop them on them), all upgrades are identical besides the two support units- which are functionally identical, and now the only reasons why I'm still playing are because of boobs and a morbid curiosity regarding where this is all going.
Mochigames is ridiculous. Not only do you need to go to a different site to see what half the skills are, you have to pay for them, too. I'm not nearly interested in flash games enough to pay for what ought to be available in the first place.
My favorite character ended up being Flies. I was able to just shoot through so many levels with those buggers (Flying+Fast), and still stop to kill bosses.