Works fine here. Been running SP2 for weeks now. The current version of DX9/0c is the same one that is in the SP2 beta. I've tried most of the beta nVidia drivers and haven't had any issues. I've even run FarCry with the SM30Beta Path and had no issues other than I couldn't load some of my saved games.
Edit: I'm actually using RC2, didn't notice you said RC1 in your post. I was running R1 without any problems though.