Motion requires that you understand how a computer works, and so do all of the pro applications. They are called "Pro Applications" because mostly professionals or those who are working towards that use them. If you're in the catagory, then you'd probably understand that Motion is a complex program that is capable of amazing things if you use it correctly. Obviously there is something you are doing wrong, or there is a small technical glitch in what you are doing if it has those problems. I am running Motion 2.0 on a powerbook, not even the latest ones, it has a 32mb video card in it, and it works great. If I overload it with filters and huge images, then sure, I run into all kinds of problems. But ****, right now I am created a 15 minute piece in motion, and its working great. If you are having problems, don't just automatically assume it's apple's fault. User error is most often the cause. Try reinstalling it, run regular maintenence on your computer, update your computer via software update, and see if that solves the problem. If not, then come here and ask for detailed and specific help.
Sorry if that seems like a rant, I'm just tired of coming here and seeing amatures complain because they don't know what they are doing and don't ask for help in the correct manner.