I have an account w/ them, but have never won anything.
Proxibid isn't an auction site, like GB. It's a proxy bidding agent/service. Basically they submit bids to auctions on your behalf. They have relationships with a lot of different auction houses and serve as a proxy for all sorts of auctions, beyond just firearms.
For example you can bid on Rock Island auctions through Proxibid - though you can do the same directly through RIA online.
So the thing to keep in mind is that the auction terms and costs can differ by which auction house you're bidding into. Also you might be able to save on fees if that auction house enables bidding through their own service, like RIA.
