I have recently had a interesting experience trying to get our new Win2K8 Hyper-V machine running right.  During the process of trying to get it up, I discovered there were a couple of key things that needed to be done to get it to function right.  I thought it would be good to share out the pointers I took down for other people who are getting theirs to work right.

1. After Hyper-V feature installation, install KB950050 patch for Hyper-V.  Note that after installing this patch, you probably need to re-run the integration services setup to upgrade all the drivers on the virtual machines.  So it might be a good idea to install before installing any virtual machines.  Also note that upgrading the drivers causes the NIC settings to disappear (which is also a pain if you have many machines).
2. Need to uninstall current Virtual PC VM additions before adding VHD to Hyper-V console.  If not, you will get an error when trying to start the image.
• A neat trick I picked up from some of the forums is that you can use VirtualPC from your own desktop machine and map to the VHD image over the network to do this.  Disable undo disk first.
3. After installing the Hyper-V integration services component.  A new NIC will be created.  You need to set back the IP settings to the original ones (which can be a pain if you have a lot of images).
4. Mouse and keyboard access is not available through RDP without the integration services component.  You can install the RSAT tools on your local client machine to access the Hyper-V images directly (download them from Microsoft as required for the type of client OS you use).
5. Need to exclude the path of the Hyper-V images from the virus scanner.  Otherwise will have errors when trying to start the machine. (After applying hotfix KB950050).  It might also be a good idea to disable scanning on .XML and .VHD extensions.
6. If you hit this error while installing integration services to a VPC. “Setup cannot upgrade the HAL in this virtual machine. Hyper-V integration services can be installed only on virtual machines with an ACPI-compatible HAL.”
1. Open Device Manager
2. Under the Computer node remove Standard PC.
3. Reboot
4. Eject and reinsert the Integration Services ISO (or rerun the setup directly)
5. When you can’t remove ‘Standard PC’ in device manager, you can attach the VHD to an running Server 2003 machine.  Obtain you windows setup CD.  You should then change directory to the \WINDOWS\SYSTEM32 directory and run "expand D:\I386\HALACPI.DL_" followed by "copy HALACPI.DLL HAL.DLL" (Reference: http://blogs.msdn.com/virtual_pc_guy/archive/2004/12/10.aspx).  I encountered this issue with an older Win2K image that I was trying to bring up.  I did this and it worked. 

For other references, Joseph also sent me this link for a good primer on how HyperV Virtual Networks or "switches" operate.
 http://blogs.technet.com/jhoward/archive/2008/06/16/how-does-basic-networking-work-in-hyper-v.aspx

If you have any other good tips, tricks or references.  Feel free to share it in the comments section.

Cheers.