I have now moved my install for the 3rd time, from one server to another, with subsequent DNS change. The vBulletin documentation has truly rocked and saved my bacon for the large "middle bit" of the move that I wouldn't otherwise have had a clue about. But there is a front and a back end of it, too, beyond the scope of the vBulletin installation itself but very significant. I just broke the code on the rest of the method, courtesy of a smart guy. Here's what I learned, 3rd time was the charm, avoided any real downtime this last move during DNS propagation, and no two-installs-out-of-synch issues. Provided here for other semi-Luddites out there. This is master-of-the-obvious stuff to many of you, but it was VooDoo slick to me.

Concept: adjust old install to point to db on new server during "transition" period when DNS may be pointing to either site (new or old)

Steps:
- confirm all install files are in place on new server
- adjust config.php for new server
- turn vBulletin off on old system via AdminCP, stopping changes to db
- backup and copy database, using detailed instructions here
- change config.php of old server to point to new db on new server
- test old server w/ new db (domain name will still get you there)
- turn old install back on via AdminCP
- test new install (need to use direct access URL to get there)
- turn new server back on via AdminCP (direct URL access)
- ready for DNS change at registrar