Being a Microsoft employee means eating our own dogfood. No not Kibbles 'n Bits, but using all our latest technologies, long before they RTM. A lot of people as what it is like working in such an enviroment and as a geek, I love it. I love working with the latest OS and software, even if it doesn't have all the features or functionality yet, and even when it doesn't work as expected.
One resource we have is called the IT Showcase and it is a great resource for information on how Microsoft does IT. There is a great set of resources there on internal learnings from our experiences running Vista, Office System 2007 and Exchange 2007. So if you are just curious, or if you are planning your own deployement, check out the IT Showcase.