Those of you out there using Linux on Hyper-V will be happy to hear that you can now get mouse drivers for Linux virtual machines that provide integrated mouse support.  You can go here: http://www.xen.org/download/satori.html to download the drivers and get going.

I also recommend that you read Simons blog post about this release here: http://community.citrix.com/blogs/citrite/simoncr/2009/03/24/The+Tale+of+an+Enlightened+Mouse

Cheers,
Ben