So I am in the process of going through an Active Directory 2008 R2 upgrade to Server 2012 which has been going very smooth so far. So far I have prepped the domain and forest and added two new Server 2012 Domain Controllers and transferred the FSMO roles from the Windows 2008 R2 Domain controller. Migrated DHCP pools and created failover pools in a load balanced mode (default) which is cool. Hard to believe it has taken Microsoft this long to get something like this to work. :( The next thing on my list was to get rid of the Windows 2008 R2 WSUS server which is deployed via a GPO out to all clients and get all clients reporting to the new Server 2012 WSUS server. Well this did not work initially because the GPO was using http://wsusserver for checking updates and reporting. For a day and a half nothing was reporting at all. Come to find out (RTFM) WSUS 4.0 uses port http (8530) and https (8531) so the GPO needed to be updated to http://wsusserver:8530 and now all clients are starting to populate into the new WSUS server. Now onto the next bit of additional testing and implementation phases.
I will be updating this post with additional notes and such as I go through this upgrade process. So stay tuned.
Update: 07/31/2013 - All has been good so far. I actually just demoted my Windows 2008 R2 domain controller in preparation of decommissioning it.