I bought a Nikon 50mm SLR lens used and it's as good as new. No scratches. The person that sold it was honest about it being in a "like new" condition. Only thing not new about it was it wasn't sold in it's original box.

I would prefer to buy my lenses brand new, but sometimes it's just too expensive. If anyone does buy a used lens, I'd suggest testing it out before buying. I got mine at a Camera Retailer.