After borrowing a D7000 for a day I gave my daughter in-law my D90 and got a D7000 body. Others have have described the improvement in quality which is quite noticable.
As to glass I never understood the dont bother using FX lens on a DX body. If you want the best image and can afford it many of the FX pro zooms etc deliver a better picture. In most situations I would challenge people to tell me whether a picture was shoot on a D7000 or one of the better FX bodies when high quality lens are used.
But there are exceptions like the 35mm F1.8 FX lens which is one of Nikons few real bargains.