Ok, I went ahead and turned up every setting but Particle Shadows, because it said not to use it yet. It looked really good, and very playable, even in 3D Vision. I was mostly at 60 fps, with dips as low as 45.
The only problem I noticed was I had some missing textures from time to time. Usually on the sides of a map, but it looked pure white with no textures. Is this a known bug or a lack of ram/vram? This happens with or without 3D Vision.
Also, is there a way to turn off the highlighting of cars? It's quite annoying when you go up to a car that looks awesome, and the highlighting makes it look wrong.