Appart from the geeky technology passion, The Hyper-V is a more cost effective solution than VMWARE, Hyper-V comes with Quick Migration and HA at no extra-cost, With VMWARE you have to purchase Virtual Center wich is at least 3 times more expensive than Hyper-V. I know, I know, "What about vmotion", well, That feature only works for planned downtimes, so it is supposed that when you plan a downtime it´s in non-business hours, so what is the difference betwen <1 sec downtime and 3-5secs downtime, in a non-business time?, I think that you´re just wasting money for that, not to mention that the Physical Host Machines have to be "Similar" or as VMWARE Says, From the same processor family. Whit Hyper-V yo don´t need simillar machines to do Quick Migration. The HA in VMWARE and HYPER-V works exactly the same way, they both restart the virtual machine in case of an unplanned downtime. The difference: Hyper-V with no extra tools or cost, VMWARE Requires VMWARE HA. What about the Hot-add resources feature of VMWARE?, well if you´ll run a Guest OS that support Hot-ADD, go ahead, but if you wanna run a Server Standart, then you´re again wasting money. Well, lets imaging that we have a guet OS that suport the hot-add, What about the services in that guest?, does an SQL Server support hot-add?, does the In-House application support the hot-add?. I think that VMWARE is trying to get all the money the can in this point because they know the end is closser. System Center Virtual Machine Manager, it´s not only a converter. It´s a provisioning tool, You can convert P2V, V2V, you can manage a VMWARE Vitual Center in the case that you need those things that hyper-v doesn´t provide, can create a self-service portal, can do Intellingent Placement of Virtual Machines. and the best of all, it´s cheapper that Virtual Center or Virtual Center Enterprise.

Not to mention the technical support of VMWARE (36 HOURS!!!): http://www.virtualization.info.....ds-of.html

Plus: The long list Known Issues for a technology they claim to be "mature":http://www.vmware.com/support/vi3/doc/vi3_esx3i_i_35u1_vc25u1_rel_notes.html#knownissues

Plus: VMWARE is new to HA enviroments, for more than 10 Yeasrs, Microsoft has supported HA scenarios.

Plus: The next release of Hyper-V is going to have the same hot-add and Live Migration that VMWARE have today, the difference: No extra $$$$$

[...] Check it out! While looking through the blogosphere we stumbled on an interesting post today.Here’s a quick excerpt No sooner had Microsoft announced the availability of the public beta for Hyper-V, its hypervisor-based server virtualization technology, than VMware went on the attack, claiming its ESX Server is a comparable, but better, product. “Hyper-V is Microsoft’s hypervisor, while ESX Server is ours. But I don’t think you can really compare Microsoft’s newly announced beta offering and our product, which has been available for seven years,” Bogomil Balkansky, VMware’s senior director of product market [...]