I went to a D7000 and am very pleased I did, I get shots I never thought I could when I started.
Whilst this may not be all down to the camera body the range of colours and the IQ is definitely better than my D3100.
The other features I like are the higher resolution liveview, the twin dials one for aperture and one for shutter speed, bracketing, faster continuous shooting, dedicated WB, ISO etc buttons......to be honest it's massively better in every way
As its £300 cheaper than its successor the D7100, pound for pound it's easily the better buy