The main gripe is the digitzer. It's the only way to get some characters without depleting all of your resources. For example, it will tell you something like:
(FYI, THIS IS NOT A REAL COMBO. JUST AN EXAMPLE)
But instead of Piggy, it will give you something else instead. Scooter actually tells you that this is part of the game. You'll go crazy trying to do this again and again and it is very time consuming. This led me to think that I was doing something wrong regardless of Scooter's assurances. I think this is what people are having the biggest problem with. I think it's the only crummy part of the game. They should at least relent upon the third try, but sometimes it takes a lot more!