I think it may just be a hard limitation at the moment. I know AVByte uses the Canon 5d and 7d, and I've noticed a few examples of focus "snapping" in their videos as well, and those are much swankier cameras.
I've also encountered troubles with the 650D just being really lazy when it comes to focusing. Especially when I'm more distant, sometimes covering my face and revealing it manages to convince the darned thing to wake up. It's a heck of a lot faster than manually focusing, but boy can it be frustrating sometimes.