7D and 100-400?

That combo was my prime set. Now I use the lens with the 5DIII and only grab the 7D when I need max distance.

De image quality is great when the bird doesn't fly too fast or does not fly straight at me or isn't doing too many fast acrobatics. My 100-400 is very sharp with slow birds that fly in a straight trajectory.

I think focusing is very sluggish. (and yes I am very comfortable with all the AF custom settings)

My 70-300 was much faster focusing and was far better at tracking swallows/swifts and other extremely rapid birds. I kind of regret my upgrade...

Now I'm going to trade it for a 400/5.6 which focuses much faster.

Just remember to keep your shutter speed up.