&#62;true MS shops will user Hyper-V and true OS shops Xen<p>That is not entirely true. I'm installing a lot of VMWare systems at "true" MS shops, which choose VM for the same reason as MS (market leader, no one ever got fired... etc.) where hyper-V is still perceived as immature product. In MS shops license cost usually is not the decisive factor, and VMware is perceived as the best technology(aksi the most expensive). It is true a lot of those places run Hyper-V as well, but they don't usually host production systems on it.<p>My take on it is: MS is quite good at making development tools, Exchange, Sharepoint, systems management software etc. (generaly high level stuff) The further they are kept from the hardware the better. Most people employed by MS shops know that intuitively and they welcome the opportunity to buffer MS software from the hardware even if it costs $10k per CPU license.