I just recently bought that lens and am using it on a 30D. Still trying to get a handle on the whole Canon thing after years and years with Minolta but I think this lens is a keeper. It is fast and accurate for shooting birds in flight. As a f5.6 it does need good light but I have already managed some good shots with in poor lighting. The eagle shots posted at this site came on an overcast day handholding this lens.

Also, if you go to my pbase account and go through the bird gallery you will find eagles, barn owls, sea gulls, and kestrels all taken with it in the past week or so.

www.pbase.com/jhuddle/birds