I just tried MDFB-080914 on the 638 Release with my IXUS 800IS with ISO100 and flash on and according to the web based test I get around 250-270ms delay which isn't so good.
This matches the results I was getting when trying to throw things past the camera. It would react, just to slowly to actually capture anything.
Any suggestions? Thanks, I only found out CHDK can finally run on my camera yesterday and I'm incredibly impressed with what can be done.