Believe it or not, I look at the sellers feedback more than the pistol. I've bought two Glocks recently that I spent zero time looking at. One from billybob44 and the other from Disposable Heart. Both have fantastic feedback and honestly described their firearms. Any gun show buys I look more at the outside for buggered screws and general condition. Buggered screws are a sign of a tinkerer. Don't even get me started on stippled polymer frame pistols.
Great points. Buy the seller is big on my list. I'll have to remember the buggered screw thing as well. I don't know that buying used is something I'll do very often but all of these tips so far have been extremely enlightening.