That's good to know, good information.
I am building a new vCS server because I need to change the underlying operating system as well; so i'll have a new vCS 6 VM on Windows Server 2012 R2. Because this is not going to be a in-place upgrade, the new vCS has its own SQL DB, etc. We'll have 2 vCS servers running for a week or two.
Good point about licensing, VMware will give us 60 days to run in trial mode before I have to switch keys. For Veeam I have the 3 Host / 2 CPU license, it shouldn't be an issue because because we have our Production/DR site, we don't backup the DR; so during my "test run" in DR Veeam won't be affected; only when I move my Production hosts to the new vCS.
When I switch my 3 hosts in Production to the new vCS, i'll need to update Veeam and point it to the new vCS 6 VM. From what I gathered here, at that point because it is a new vCS I will need to do a full backup. Our Nightly jobs are setup as Reverse Incremental (we offload to tape and need full backups every day to be taken off-site).
So the only things to take away are a) Apply Update 3 and b) Full Backup when switching vCS because it has a new ID thing.