I've heard the Nikon 70-200 VR, while a great performer on the DX bodies, falls off badly on a full frame. I don't know anyone that has one though and that's a lens I've not used. On the other hand the Canon 70-200 2.8 IS provides fairly uniform performance on a full frame, but supposedly isn't as sharp at the center. So I've heard... and seen in a few tests. I'm still using my old 70-200 non IS model. Predates all this IS nonsense!
Maybe, I haven't tried. I have a D3 and my 80-200 AF-S works well on it, normal vignetting that Photoshop easily removes. I don't have a Nikon 70-200 VR anymore, but I'll keep that in mind next time I'm out on a gig ... there's always somebody next to me with one, and I'll take a few test shots with it.
Know what the absolute sharpest and most saturated lens I've ever owned is? This will be a shocker ... a Tamron 28-75 f/2.8 that I had recalibrated by the factory (they did it for free). It literally is sharper at 50mm/2.8 than my 50mm f/1.4 is stopped down to 2.8. And it has just ridiculous contrast and saturation.
I'm a Pro Sports shooter, so I know longer lenses ... and the Sigma 120-300/2.8 is my favorite sports lens ever.
So I kinda get a giggle when people try and compare Nikon vs. Canon lenses. Some of the best lenses on the market are 3rd party.
I just used the new Tokina 11-16/2.8 the other day, I think it might be the one that persuades me sell my Nikon 12-24/4. Another incredibly good 3rd party lens.