While at Convergence last week, Microsoft went ahead and released Update Rollup 3 for CRM 4.0. You can get it here.
A few important notes:
- Importing and exporting customizations is supported between servers with Update Rollup 2 and 3, but not supported between Release, Rollup 1 and Rollup 3.
- The CRM for Outlook Client has some memory usage issues resolved.
- Performance issues with CRM related to the email router have been resolved.