I have at least one unusual multi city trip per month and I do not have the patience to surf the net for those type of flights.
So I work with Donna or Elle at Travel the Rainbow, 800-777-8747. They are on the east coast, don't charge any ticket fees and always seem to find a flight cheaper then I can.
Big thing for me is that after they book my flight/hotel/car it is posted online and then I can download it to my PDA. Very important because I hate paper!
I still book the basic flights online, but if you want to have a "just in case" number, they have been good to me. I wonder if I should tell them I just posted their number online.

Oh well.