I'm going nuts practicing on BIF. My Sigma 100-300 f/4 AF isn't quite up to the task.
Just waiting for Arash's 400/5.6 to come by FedEx (I know, by looking at his stuff, that I won't be able to blame my failures on the glass :p )
Anyway, here's an attempt with mine. I probably shouldn't have stopped down so far, but when I don't, I usually miss the focus entirely while the AF catches up. Is the BG too distracting?
Canon 7D
Sigma 100-300mm f/4 @ 300mm
1/600 sec @ f/11
ISO 320