I wouldn't criticize the lens for that first shot - catching a Bushtit in midflight is an accomplishment enough, even is it isn't tack sharp - those little buggers are fast. The Fox Sparrow was a lot more cooperative, though.
How can you hold a lens responsible for digital noise - isn't the camera's processorresponsible for that?
i don't blame the lens for noise... that's the sensor. i had just thought the 40D was a bit better than that at high ISO... i've been having some focusing issues with the lens, and i'm trying to determine whether it's the lens itself, or just crappy light... no AF system works well in the gray, dreary light we have here most of the winter, but this lens seems to have some issues even in what passes for sunlight here this time of year... maybe i'll just have to wait till spring to see if it's working right...