I updated the server last weekend. I was wondering a lot of things before I did it:
(1) Would my old license file work with the new one? I figured no, so generated a new file for the latest version of Creo (8.0).
(2) Would the license, once updated, work with older Creo. This, as you noted, is a big "yes". Works fine. I was mostly concerned about the non-standard modules we have had for decades. They worked fine.
(3) Would I have to remove the old license server completely before putting on the new one? I assumed yes, and did this, killing the pertinent services before doing so. It worked fine, too.
(4) How would all this stuff work with a virtual server? Perfectly fine.
So, in all, not so bad. Only little difference between what I remember is you don't install the license server as a choice in the normal "setup" program, there's now a separate "install_license_server" program to use. It went very quickly and all is well.