I use Eurail passes (almost) every trip to France/Italy. One year I skipped the pass and took three budget flights Paris-Venice, Venice-Palermo, and Pisa-Paris.
I prefer the passes for several reasons: FLEXIBILITY (I can schedule my travel after I arrive in Europe and re-schedule as I go along), EXPENSE (I may not save money, but it feels more economical for most trips when the cost per day is averaged out), travel during my PREFERRED HOURS (cheap flights all got me out of my hotel in the dark early hours in order to get to the airport 2 hours before flights), and VERY IMPORTANTLY I like to meet and talk with people on trains.
Advantage vs. point-to-point: I like to pre-pay my trip as much as possible. I will pay point-to-point for short trips. With a pass I sometimes just hop on a train. Being impromptu sometimes is fun.
In the April 2007 "Budget Travel" magazine there are details concerning train travel deals. Plan ahead; rail websites offer specials.