I always wondered where those "refurbished" bodies come from. Not sure I buy the "salesman's sample" line some retailers use. If you've ever been to a place like BestBuy or Costco and seen camera bodies chained to some display - WITHOUT any lens mounted (the sensor open to whatever is in the air and who knows what kind of abuse)...... not sure I'd want THAT body - even if Nikon service cleaned it up.
I suspect many problem returns end up getting resold this way. I had a new D200 acting odd from day 1 - and the retailer exchanged it without any issues......but what happened to the one I sent back? Don't know.
Personally, I'm not sure the nominal cost savings are worth the potential risk. Most refurbished bodies only come with a 90 day warranty - I don't know if youy can get a longer Mack one (or if you can, if the additional cost offsets the savings).
If there's not much of a difference...... I'd go with new - esp since D80 prices seem to be dropping.....
One other option - some local camera shops take equipment on consignment and have good equipment at reasonable prices, often stuff they originally sold. A little less risk than buying used blind.