A Vista compatible client for CRM 3.0 has been released

You can download it from here.

There has been a lot more added to the "V3C" update than just Vista compatibility, such as:
- Integration with the Office 2007 “Ribbon”
- Custom MAPI Store (no more PST file!)
- SQL Express Edition 2005 SP1
- Inclusion of all existing client hotfixes
- Windows Vista Support
- User Access Control
- GPO deployments
- Internet Explorer 7

You can read the general announcement here.