Microsoft has just posted a somewhat repackaged case study for Groove, TeamDirection and Steelcase. It's actually based on the Groove 3.x system, but its been a nice customer solution for everyone involved.
The bottom line:
Steelcase groups using Groove Virtual Office (and TeamDirection!) saved up to 10 percent on project costs by reducing travel expenses and increasing productivity.
I think the same type of solution will also work very well for SharePoint users too.