I will agree with this. The D50 is one of the best consumer Dslrs out there. If anything I would go with the D80 over the D60 it leaves you open to use all of Nikons glass with full functionality. What is the D50 not doing for you that you feel you need to upgrade?I personally wouldn't. D50 has a built in focus motor, D60 does not.. D50 has a top lcd display, D60 does not. Those things are deal breakers for me. Most people probably wouldn't agree though.
If that's not an issue for you. The ability to crop closer because of more pixels, and the smaller body size, larger lcd, might be good reasons to upgrade.