Hi Phil,
I have an EFW2, from experience the EFW2 design rotates one way only. The filter software reports back to the application the state - including when it's transitioning and when it's completed it's transition. This information is exposed on the Windows SDK.
I take it you're imaging rather than using it for visual?
There are several sources for drivers - ATIK's own Windows SDK, INDI where Cloudbusters have implemented OS X and Linux, and mine on OS X. The source for the drivers is closed source, both Cloudbusters and I have signed NDAs in the past todo this.