Hi I completely understand your frustration. I own the Nikon D7000 too and came across the focusing issue before. Don't listen to those who says user error, this is completely camera error. I even could not get a sharp image in good sunlight with at least 1/2000 sec of a building or any subjects. I sent my back to Nikon to repair, they fixed it more or less but having issues with my 18-105 lens, it does not focus consistently on different focal lengths.
For example @50mm it's pretty ok but at the ends it's just not there yet.
Those who says user error I would mention that using the live view mode I can make tack sharp images...
So I also considered moving to Canon, only reason is that I mainly shoot sports and I read lot of good things about the Canon's white magic 'L' lens of the 70-200 f4. The Nikon 70-200 f2.8 version would cost appr. 3-4 times more for which I do not have money. Also the Canon's lens park is really good, their 'L' lenses costs less then a similar Nikon lens so having transferring to Canon I could make a good choice of lenses for a reasonable price.
I had a chance to try several really good lenses from Nikon on my D7K body, like 85mm f1.4 or the 24-120 f4, 105mm macro, but these costs a fortune. These lenses just amazed me and it seemed my Nikon worked with them really good and the pictures were just razor sharp...
The only drawback to moving to Canon would be the price again, the body I would buy is like the 5d Mark II (or the III one) or 7D, but these would be expensive though.
My other idea is to sell my D7K and buy a used Nikon D90 and I would spend the difference between the bodies on a good lens (like Sigma 70-200)...
Not sure if I answered your original question at all but at least wanted to say I'm with you with your D7K focusing problem and I have gone through the same pain that you did (like calibrating lenses, shooting idiot test shots checking focus accuracy...)
Cheers,
Bela from Hungary