IMHO you don't need an FPU for some objects who are moving on the screen. At least we have some definitive pixel data to put the objects at (nothing like 0.43567234129 pixel from the left or else). And you won't mind if a ball flies across the screen with 280 or 280.53429921 pixel per second.
No matter if there are physics around or not. What thomas said was quite correct: The MOST time consuming part is to calculate the graphics/animation. The movement itself is just a poop, at least in assembler or fine coded C. The interaction of the thingies in Angry Birds is nothing more and nothing less than pure calculation, it doesn't matter that much on which algorithm it depends. I think what many people forgot is how fast a computer can calculate if it's really pushed to its limits.
Besides, Angry Birds isn't really much fun. It's just a good demo for tablets.
My 2 cents...