Whether or not Priceline will ALWAYS beat Hotwire is pure speculation. Besides, the advantage of Hotwire is that it is an upfront pricing service; no guessing as to whether or not you're bidding too much.

On the issue of weekend trips, I bought a Hotwire ticket from ATl-DCA for $140 r/t, with an early Fri. afternoon departure and a Sun. afternoon return on CO. Very respectable.

The lowest published fare for travel on those days: $279.00!!! So I saved MORE than 40%.