Just a couple of days ago Microsoft released the source code of its Linux Integration Components for Hyper-V under the GPLv2 license.
Only time will tell if the integration of these paravirtualization drivers into the Linux kernel (something that is under evaluation) will translate into a concrete benefit for the Microsoft customers.
For now the priority remains to have the two most popular enterprise distributions, Red Hat and Novell, inside the Hyper-V virtual machines. And Microsoft didn’t help much about the former so far.
Things are changing anyway : the new R2 version of the Linux Integration Components will finally support Red Hat Enterprise Linux 5.2 and 5.3.
Unfortunately they still lack the support for mouse integration, that must be provided by the Linux distributor, and they still only support virtual machines with a single vCPU.
The Linux Integrated Components R2 will be available for free for both Hyper-V and Hyper-V R2.