I have used them and haven't had any problems. I always look at the dealer ratings and any comments about the dealer. If they have a lot of ratings they have been selling a lot on the auction and should be stable businesses.

I've used them quite a bit and haven't had a major problem yet. I had one minor communication problem with a highly-rated dealer, but he claimed he had problems with his e-mail for a while. Some dealers (eg: Bud's Gun Shop, S&S Firearms) seem to do a huge business on Gunbroker. But like on eBay, however, be very cautious of dealing with individuals, as opposed to dealers. Although I must say I've worked with some wonderful individuals for magazines and such through Gunbroker.

Also, if you're buying firearms, be VERY mindful of Federal interstate transfer rules, and follow your transaction every step of the way. Get tracking numbers, then follow them so closely that you'll know your FFL dealer has signed for a delivery before he even realizes it. Then go pick up your merchandise right away.