I also use Orbitz, Travelocity and others for research and then book directly with the airline. Keeping a middle man out of the loop is important if something goes wrong and I also get bonus miles for using the airline site. They also sometimes have unadvertised specials on their site.
As Delta and American, my usual airlines, have a low fare guarantee, there is not much reason for using Orbitz or others. One caveat, I think Orbitz and maybe Travelocity do have a money back deal where if the price goes down for the flights you booked, you get the difference in price back.
The only time I don't use AA or DL sites is for the last minute specials where a package deal on one of the travel sites is usually a good deal.
Cheers