Shun Cheung , Dec 04, 2010; 10:57 a.m.
I have not experienced any problems with my D7000; including no back focus issues, but I only have experience with exactly one sample.
I also should point out that I am very picky about AF accuracy so that I tend to use 1 of the center 9 cross-type AF points in most situations. I have experienced AF issues with the outside, line-type AF points. But having AF issues with line-type AF points is a common problem on all (Nikon) SLRs, including the D3 family.