Aside from this game being really grindy (more so than other upgrade games), what makes it really frustrating is that you receive no money at all for failed missions. Depending on how close you get to completing the mission objective, somewhere from 25%-75% of the money would be nice for a failed mission.
This game needs something that shows me how much health I have left after I lose my windshield. An option to turn off the gore would be nice as well since my computer sucks and the blood spatter slows the game down.
Thanks for making a save point after every challenge and during the stages of the boss battle. I dislike games where you have to start killing the boss all over again after you die.
I like the different bird species and how they each have special skills. I also like the fact that I can change the pecking order to suit my playing style. However, some sort of radar upgrade would be nice so my flock is not constantly wiped by by planes coming from behind.
I got tired of the bad movement and wonky firing at about level 3. When I move I should immediately move instead of having a half second wait until I'm actually moving. One apparently can't escape zombies in this game unless they have Mercury's sandals.