bought a used D300s on ebay 3-4 months ago, but haven't had the heart to get rid of my D80 yet... lol
Doing basketball I actually threw the 70-200 2.8 on the 300 and an 18-70 on the D80 and worked both ends of the court.
I think you will find that the D300s will be your go-to camera, once you get used to it. I've never had a D80, but from things I've read, that particular body had some issues with the metering system. Not that it didn't work, it just worked differently than prior bodies, and was not well received with Nikon owners.
If you don't already know about this guys site, check it out:
http://www.bythom.com/index.htmHe does a lot of real life reviews of mostly Nikon stuff. He also has EXCELLENT instructional CD's for the various Nikon bodies, and they are written in such a way that you will actually use some of the settings he recommends. They are PDF files, so you can print them if you want. Money well spent, IMO.