1. Unlike older install situations, you should be able to use the regular network adapter, instead of the legacy adapter.
2. I personally had better luck using a Netboot ISO : that seemed to work with the commands in step 3 better; also allows you to better customize your install.
3. At the first install menu, use F6 to access the options menu. Hit ESC, then END: you may now type in one of the following, before hitting ENTER....
prefer_ ms_hyperv= 0
4. I told the install to use the hard drive labeled for Microsoft (it offered me two choices, the other being generic). My recommendation for a filesystem: I've gotten a lot of mileage out of XFS. One issue that affects desiring to use btrfs, is how Hyper-V handles clock timing: I've seen it cause corruption in the past. EXT4 has its uses, but I'm a fan of more heavy-duty filesystems when they're available.
5. If you're using SSH on the new install, I recommend you set EnableRootLogin in /etc/ssh/sshd_config to no
7. Baseline 12.04 uses 3.2 kernels: at the time of this writing, 3.5 is available. You can grab one of the latest Ubuntu-built mainline kernels, and install them via dpkg.