One more thought... and this pertains to Nikon systems only, I know nothing about Canon. You may want to consider Sigma for a 70-200mm lens. I don't use one, but I know a few that do and they get excellent results. I have no doubts that the Nikon 70-200mm is a better lens, however, for half the price, the Sigma may be worth a shot. I'm considering a test run with the Sigma to compare it with my Nikon.
I have both the Sigma 70-200 F2.8 HSM lens and the Nikon 70-200mm AFSG-VR Lens and in terms of focusing speed there is no comparison. They are like night and day even if you don't count in the VR. But of course the Sigma is $1,000 less than the Nikon. I think the Nikon has a longer warranty though. I'd have to look it up but memory tells me the Nikon warranty was seven or eight years and the Signma was one or two years.
I used to never shoot the VR with my D70 and D70s and up until last July, hadn't used it on the D200 at all. Once I started using it on the D200, it made a dramatic difference in my sharpness. It was well worth the extra dollars. You need to work within what you feel comfortable spending though.