I am actually more than two thirds done with my upgrade process. I have 12 of 36 targeted machines left. Of those 12, only about 5 have to be rebuilt and upgraded. The other 7 are going through a retirement process or are already upgraded to CentOS 7.
Although I am, as I post, working on the mail server. It is actually already done, but I am in the process of backing up the old mail server, then I will delete it, move the new mail server from an NFS store to a local data store.
By end of week, I hope to get all but three upgraded. This remaining three will be important undertakings though.
One thing to mention is that these are VMs. The final one to get an upgrade will actually be a pretty important physical box. I want to do new hardware, but still looking at my options.