We are a lot smaller - 5 servers. I took the opportunity at easter this year to virtualise onto 2 clustered r610s with bags'o'ram'n'CPUs (tm) + MD3220 . I migrated 4 servers, exchange, sql, fileserver(profiles + shared drives), "other" (DC, WSUS, etc) from physical to virtual and left one on 2k8R2 as a physical DC (with FSMO roles). 2k12 went smoothly; spent easter setting up SAN and host + guests, then migrated fileserver and one DC. Over summer another week moved exchange and SQL.
Since I still have the old hardware I am going to start them up again on a segregated network (still outside tombstone life so they should start up ok) and see what would actually happen if I inplace upgrade to 2k12 from 2k8R2. I have never done an inplace upgrade so it would be interesting to see what would happen.
For backup we use both windows backup within the guests (for data recovery) using virtual drives and "backup assist" on the host for disaster recovery. A pair of mirrored openfiler boxes using consumer IDE drives stores our backups.
We're going with DPM as well, just rolling it out.
Our domain controllers run Windows 2012 along with our file servers and Hyper-V Servers. A couple of other sundries run it too.
We don't have a set schedule to update everything to 2012 but if a new server is being built or an existing one is being rebuilt, we'll generally put the latest version of the OS on there unless there's a specific reason not to.
We're also using DPM to back up our infrastructure. It's simple but it works. After using Commvault Simpana (Which also worked but was bloody complicated), it's a breath of fresh air.
Might be worth looking at this discussion before migrating to 2012. 2012 R2 seems unaffected at the moment.
No issues for me. Our 2k12 "file server" (profiles and shared network drives) is fine. No issues on our exchange, WSUS or DC.
I did have a very similar issue with out WSUS 2k8 server some time ago. This server would work if I used the IP address but not "servername" in the UNC. I cannot remember how I resolved it but I have a feeling it was either DFS (in that implementing DFS made it go away) or DNS related.
I've done most of them here. Just the MIS that is supported externally so I wont touch that, and an old 32bit server still on 2008.