Lately I have bought most everything new. Years ago, I bought a 300/2.8 Nikon lens and a Nikon 1D ($5000 new at the time) on eBay. Both of the sellers had a high number of feedback ratings and were 98-99% positive ratings. I felt like if this many other people had good things to say then I could trust the seller. Both times the equipment was in perfect condition and the sale went off without a hitch.