Microsoft has made the long awaited Windows Server 2003 SP2 available as a release candidate (read: beta, broken, not for production) with some fairly interesting and worthwhile updates.
MMC3 is going to be a must for those that will be early adopters of Exchange 2007 but most of the improvements are going to be a hard sell initially. I can tell you from experience of thousands of Windows Server boxes we manage that they are rock solid and have performed remarkably well. Still nice to see Microsoft continue development on its flagship server product and adjust to the market needs. Niiiice.