As said before if anyone really thinks you have a problem with your gear (ie backfocussing etc) then its very simple to do a controlled test - DO NOT TEST ON A PERSON OR A MOVING OBJECT OF ANY KIND OR HANDHELD
Use a tripod, or put camera on a steady surface, a table etc
Use either a remote release or the timer
Make sure you focus exactly on the object
line up a few objects in front and behind the main focus point (use cans or boxes etc) or a focus test chart (google it)
use flash so that your s/s is at least 1/200s
Shoot JPEG
Shoot at ISO200
etc
Do a controlled test before even thinking about blaming cameras or lenses for OOF shots
Story - about a year ago a friend had bought a brand new d300 with 24-70 lens as she claimed her d80 and 18-200 was too soft. I could still use her old gear and get sharper shots, and her d300 and 24-70 and get nothing sharper. She couldnt get sharp shots with either combo. Its hardly ever the equipment