Several things put me off Hyper-v:
* No memory overcommit (4gb allocated to a VM takes 4gb from the pool) BIG issue for me and HA.
* No pagefile consolodation.
* 2008 Ent or Data needed for some slightly advanced features.
* It requires SCVMM for advanced management features.
* It requires 2008R2 and SCVMM for CFS and more than 1 VM per lun.
* It requires 2008R2 and SCVMM for live migration.
* It requires SCVMM and
SCOM for DRS (like feature).
* It requires IE7 and other totally unrelated updates.
* Nic teaming is not native, 3rd party drivers and setup required.
* Only suse 10 linux is supported (and windows back to 2000)
* No shared ISO storage, it makes a copy for each mounted iso.
* No USB passthroughs.