FreeBSD installs without any issues if you add Legacy Network Adapter, instead of standard one in VM settings before install. I used ISO file 64bit FreeBSD-9.1-RELEASE-amd64-dvd1. I assume the 32bit would have the same procedure.
update: out of box there are no Integration Services (heartbeat, time, reboot, etc..), but there is a patch that MS is trying to incorporate into FreeBSD / refer to https://github.com/FreeBSDonHyper-V/freebsd/wiki/Build-the-kernel-with-the-HyperV-drivers
the patch is sort of ready for 8.2 but not yet for 9.1, anyway this is what you can do to try to add hyper-v support in 9.1, run:
# pkg_add -r git
# cd /usr
# git clone https://github.com/FreeBSDonHyper-V/freebsd-head.git
# cd /usr/freebsd-head
# make buildworld
# make buildkernel KERNCONF=HYPERV_VM
for 8.3 or 8.2 follow the instruction here http://buchizo.wordpress.com/2012/09/12/freebsd-on-windows-azure-vms-en/
The hyper-v on Windows 8 pro will complain that network adapter hn0 is in degraded mode and that integration service upgrade required.