I have the 400VR 2.8 lens which has caused me nothing but trouble. I bought this lens new for $8200 at Competitive Camera about 3-months ago. I was at a paying gig on its first outing and apparently I didn't connect my D3 to the lens correctly which caused the lens mount to strip. I had the mount repaired back then. Now, another paying gig later (today) my lens started to flutter in and out, trying to hunt for focus in a rapid pace. I've never experienced anything like it before. First of all, IMO I believe that Nikon lens mount is not of the same quality as canon. Looking at Nikon, it has too many potential moving parts that can potentially go wrong or get damaged when compared to canon. The nikon mount is very cheezly made, the contact spring loaded pins can stick, which is what has happened. I believe canon is solid in comparision. I know I have a 5-year warranty for the lens, but thats not the problem, I bought this lens because I need it for shooting several times a week for several paying gigs. I now have a very tough decision to make about paying someone locally to fix it in a few days or send it Nikon for repairs and wait several weeks, which means I will loose more money by not working. The worst part or humilitation of it was I was hired to shot a soccer gig locally and had to use the vendors mk III & 300 IS to shoot the gig while my 400 sat in my truck. If I continue to have problems, I will simply sell off all my Nikon gear and switch back to canon, since I have never had a problem with canon, other than the mk III not being in the same class as the D3, but it means nothing if the gear is not functional.