AF and video... no matter how fast or silent the AF system the problem is always going to be the correct area to focus on + shallow depth of field + movement.
Above a certain level of video camera (Sony EX1 for example) video cameras just don't have AF.
I wouldn't get too hung up on it. Get lenses that can be focused manually (nice long throw focus rings, nice wide rubberised grip, non-rotating filter thread)
and get a body with live view magnification, so 550D, 600D, 650D.
I moved from a 550D to a 600D as the flip out screen was just so much more user friendly for video, and as standard audio level controls are useful for more serious work.
There isn't a lot to sell the 650D over the 600D from a video users perspective.. the 650D can continuously record accross clips which is a nice feature to have (by this I mean, the 550D, 600D, 60D, 7D, 5D2 all stop recording when they hit the 4GB file size limit - this equates to around 12min of HD recording, the 650D creates a new clip without interupting the recording) depending on your intended video application this could be a deal breaker.