I've bought some off Gunbroker before, its okay. I personally don't like buying things like firearms at auctions myself, as they sometimes tend to drive the price up in the sellers favor. Of course I think they are great, when I'm selling.
The new system on Gunbroker, although I suppose its not really new
at this date. Allows time to decide on the final bid. Its like the auctioneer saying going, going, gone. If someone makes a bid with one second to go in the auction, it automatically resets the clock to 15 minutes left, I believe. That is better than when used to, at last second someone could bid and win it. Now, you have time to decide if you want to out bid them.