I also own a D7000, moved from a D5000 and an 18-50 sigma f2.8 macro as my walk around lens.
When I upgraded to the D7k it was a much less forgiving camera with the sigma lens, because of the higher pixel count. That changed when I got Nikon 17-55 f2.8, but thats £600 s/h, I also use a tokina...