The October issue of Consumer Reports cites a test done at synchronized times on 19 of the busiest U.S. routes with cheaptickets, expedia, lowestfare and tra velocity. Fares were literally all over the place with hundreds of dollars apart.
On a particular LGA-ORD routing, Apollo as booked by a travel agent came in with the best fare and schedule.
The bottom line: I use the sites primarily for information purposes. I always check with my travel agent and mostly end up booking with him. Besides getting often the best fares, I get my seats request confirmed, and sometimes I get addl. advise I did not know. Best of all: I save lots of time compared to navigating those websites.
(rather spent my time on the FF board!)

[This message has been edited by cesco.g (edited 09-19-2000).]