The much delayed VS 2005 R2 SP1 release is getting closer to release. The biggest and best feature is better Windows Vista support. You can download the RC here.
Other noteworthy items:
Support for hardware-assisted virtualization
Support for greater than 64 virtual machines on x64-based hosts
VHD Mount command-line tool and APIs
Tested for interoperability with SCVMM Beta 2 RC
Interoperability with Volume Shadow Copy Service.
Support for additional Guest and Host Operating Systems
Service Publication using Active Directory Service Connection Points
Host clustering whitepaper
Virtual SCSI fix for Linux guests
Larger default size for dynamically expanding virtual hard disks
VMRC ActiveX control and Internet Explorer Security Zones
IVMGuestOS::Get_OSName property returns more operating system information