I had a Vitus 979 Motobecane Prolight (a/k/a "Profright") from 1986-96.
It was never my primary bike, but I rode it alot. The same thing that made it a plush ride also made it a poor racer. Compared to my Columbus SL Eddy Merckx (Molteni replica, full SR, still for sale!!), the Vitus had a lot of flex. It was light enough (very light for the time), but whatever advantage the lightness gave you on the climbs, you lost with the flex. I am not a powerful rider, and not heavy, but I have heard that heavy powerful guys could make it shift without moving the shift levers.
I have also heard that you should not leave one in a hot car.
I never really had a problem with mine. I lived near the coast at the time, and it sure was nice not to have to worry about rust.
Bob Oast
Asheville, NC