Consider the following statements together: "I'm thinking about upgrading to the D7000" and "I also need a new lens because my 70-300mm VR doesn't produce sharp results on my Dxx." Does everyone see the problem here?
No, they don't. Because I got three variants of this in my InBox yesterday. It's the "a magical new camera will improve my photography" chant all over again. Let's start with the second statement: if a 70-300mm VR doesn't produce sharp results on your current camera, you either have a bad sample that needs fixing, or your capture discipline (technique) is wanting. In both cases, you need to deal with that problem first. Updating to a camera with more pixels may actually compound your problem, not fix it.
People just want a new camera, so they look for reasons to justify it. Unfortunately, the reasons they propose should usually lead them to the opposite conclusion, though the fog of marketing lure seems to make them unable to see that. It's new! It must be better! If it's better, it'll make me better!
This isn't to say that the D7000 isn't a good camera or that it won't improve some photographer's lives. I imagine professional travel photographer Bob Krist is in love with his D7000, for example, as there are plenty of features and qualities for him to exploit that go beyond what he could do with his D90. (Yes, some pros use consumer cameras. Don't act shocked.)
So be honest with yourself. You either need or you want a new camera. If you need it, you'll know why and the questions you should ask me and others should be very pointed to the specific thing that you need to be better. If you want it, you don't need to ask me anything. Just buy the darned thing and get your lusting over with (assuming you're not piling debt upon debt to get it). Then get yourself to a Consumer Anonymous meeting and start the twelve-step stop-buying-everything program before your closet fills up with unused gear and your spouse locks you out of the house.