I have tested Hotwire extensively over the past few days. I'm not at all impressed. I used as my test routes winning Priceline bids that have been posted over the past week or so to the Priceline bidding board that I host. In 100% of the cases, Priceline won out.

jAAck, I'm not sure that your IAH-MIA example is a worthwhile one. Airtran serves HOU-MIA. What is their fare for the travel dates you searched? $400+ is certainly not an indicative fare for that route on an advance purchase basis. Were you using Labor Day weekend by chance? And how did the $186 fare compare to what may have been available at http://www.lowestfare.com and http://www.cheaptickets.com, both sites where you can see your entire itinerary before you commit?