I was taking a look around for some Hyper-V performance guidelines when virtualizing production workloads such as Exchange 2007/2010 on Windows Server 2008/2008 R2.

Checklist: Optimizing Performance on Hyper-V
http://msdn.microsoft.com/en-us/library/dd722835(BTS.10).aspx

Looking for that last ounce of Hyper-V performance? Then try affinitizing your VM to a NUMA node
http://blogs.msdn.com/tvoellm/archive/2008/09/28/Looking-for-that-last-once-of-performance_3F00_-Then-try-affinitizing-your-VM-to-a-NUMA-node-.aspx

Hyper-V Performance Counters - Part five of many - "Hyper-VM VM Vid Numa Node"
http://blogs.msdn.com/tvoellm/archive/2008/09/29/hyper-v-performance-counters-part-five-of-many-hyper-vm-vm-vid-numa-node.aspx

Performance and capacity requirements for Hyper-V
http://technet.microsoft.com/en-us/library/dd277865.aspx

Microsoft Support Policies and Recommendations for Exchange Servers in Hardware Virtualization Environments
http://technet.microsoft.com/en-us/library/cc794548.aspx

Exchange Server 2007 and Hyper-V
http://blogs.technet.com/scottschnoll/archive/2008/06/15/exchange-server-2007-and-hyper-v.aspx

Should You Virtualize Your Exchange 2007 SP1 Environment?
http://hypervoria.com/hyper-v/should-you-virtualize-your-exchange-2007-sp1-environment.aspx

Hyper-V How To
http://blogs.virtualizationadmin.com/davis/tag/hyper-v-how-to/