Just to remind you, my focus sensor went South on me. Nikon won't say whether it was a mechanical failure, a software failure or just dirt. They said they "cleaned and adjusted it". They also "adjusted" my 70-200 f/2.8. Total cost was just under $300.
On the way home, I stopped by the roadside and shot some test images which I plugged in when I got home. You be the judge (all images converted to jpg and reduced in size to reproduce here):
This is a 2000px x 1300px crop out of the frame. I deliberately shot it at f/2.8
This is 3000px x 2000px approximately, shot at f/8 which is, I figure,
the sweet spot on the lens
This one is a tighter crop: about 950px x 650 px, so it's almost 1:1. I shot this at f/2.8 and the tractor was coming at me at about 50kph. I shot at 200mm, when he was about 200m away, using the continuous focus function.
I also have an image of a barn (tack sharp) and a police car going away from me at about 100kph (you don't think I would be dumb enough to point my camera at a police car coming towards me, do you?). When I shot the car, he was at least 300 or 400m away and I can tell you that his license plate renewal sticker says "JUN 12".
I'm a happy camper. I don't think my camera/lenses have been this clean EVER: even when I got them! (I really don't want to put the UV filters back on, but I guess I have to!).
I highly recommend sending your stuff in for a general cleaning/adjustment from time to time. It's worth the money. Read more in my tech blog here. By the way, I don't know what they did, but even the white screened paint on my lens (where the VR switch and others are) is fresh and new: they must have replaced that piece because the paint was worn by usage!
Good customer service deserves recognition. Nikon Canada: you have my vote!
PS: the lens hood on my 24-120 wasn't latching on because it was worn. I asked to buy a replacement. They GAVE me one.