I used Hotwire for a Christmas holiday trip from AUS to DEN. This is a high fare market (best I could find was $350 on connecting flights, and about $450 on the UA nonstops). Also, the latest sale didn't help, because it was only good til Dec 14 and travel wad Dec 24 to Jan 2.

Paid $208 on Hotwire, including all taxes and fees, and got a routing on AA through DFW with normal connection times. Since the lowest fares in the market were connections, and this was $150 cheaper, it was a great deal.

But looking at other markets, Hotwire doesn't seem to offer very good deals.