No experience, but there is some who firmly believe that the ATI cards are not the best to use with SW. They (ATI) have had (have?) a history of not updating their drivers on a regular (or specific) basis.
Otherwise, I would assume that you wouldn't experience too many problems, but if you start getting dumped for no reason, or your screen freezes for no reason, then you will know.
Let's say that if I have to choose between 9700 and for example PNY QUADRO 4 380 XGL 64MB, I definetly would choose PNY. Ok, the 9700 is good also, but Quadro 4 -series is fully designed to 3D-Designing. If you need to see the more tests of those check
We tried the 9700 as a temporary fix when our video card went out and SolidWorks would lock up within a few minutes requiring us to end its task. We replaced that card with one of the FireGL cards and had no problems. As far as cards and SolidWorks go we have had the best result from the Quadro4 900.