Damn. The rate at which you earn new weapon upgrades is terrible. I don't wanna shoot one bubble per second at level 10. Gimme 4 machine guns at that level. I just wanna blow stuff up. These feels like an endurance challenge without the challenge. It's just incredibly tedious.
The AI is terrible. I don't mean that they jump off cliffs randomly (even though they do), but once you reach about 7-8 kills in Survival mode, they know your moves before you even do them.