Hello. I'm looking to get a 70-300mm ish lens for my 350D, and I'm stuck deciding between this Sigma and the Canon 75-300 USM. I know this was asked not long ago and the answer was resoundingly the Sigma, but I've got a more specific problem with deciding. I've seen tests / sample shots where the Sigma is better optically, plus it has 2:1 macro capabilities which is handy. However.... I've also heard that the Sigma is slow to focus and hunts around in low light. This could be a problem 'cos I want to be able to use it occasionally for sports / cars / planes / wildlife (birds, etc) i.e. things which move fairly fast. I've had a play with the Canon and was very impressed with the speed of it, but I haven't been able to try out the Sigma. What I want to know is what are people's experiences with the Sigma's focus speed / accuracy? Is it quick enough to use fairly reliably at motor / plane / sports events? How usable is it in low light? Ta, Scott.