I saw this article a couple weeks ago

http://www.tek-tools.com/wordpress/index.php/214/virtualization/3-ways-to-get-the-most-out-of-virtualization 

and I wanted to highlight it because it really addresses issues that most people forget, the non-technical areas that drive a virtualization deployment.  I think that often there is a little too much focus on the technology and not enough on the implementation, such as integration with existing processes, personnel, and groups.