Upgrade from D5100 to D7000
Going to a D7000 from a D5100, while an upgrade to be sure, is not a large one I would consider worthwhile. I usually advocate going with the best value option available today, but in this case suggest holding off if you can for an upgrade of the D7000 line (D7100 possibly). You'll then get (in all likelihood) the next generation sensor advantage to go with commander mode, pentaprism VF, inbuilt focus motor(if it remains), more direct controls and all the other benefits.
An alternative is also the D300s if you can pick one up at a good price - pro build and handling all round to boot (if not the latest sensor tech).
Cheers, Rob. http://www.flickr.com/photos/robsouthoz/