The Enterprise Engineering Center (EEC) has put together a paper on running SharePoint on Hyper-V. It has a lot of great information, including links to required reading on Hyper-V, configuring and optimizing Hyper-V, key updates to install, and disk selection. It goes into the details of the tests as configured on actual hardware and virtual hardware for both small and medium sized farms. The papers contain a number of links to other relevant topics, including the Microsoft Assessment and Planning Toolkit (MAP), Hyper-V Planning and Deployment Guide, Step-by-Step Guide to Getting Started with Hyper-V, and a bunch of links to blog posts and other resources on Hyper-V performance. Good stuff.