I had forgotten what a pain in the ass a major upgrade can be... Made even worse by switching platforms, going from a PowerPC based Mac to an Intel based one.
I did a number of 'test compiles' on the Mac Mini just to make sure that things looked like they'd be working come Leopard day, and figured out that in order to clone my old server over to the new box, I'd have to format the drive with a GUID partition map, something not done by default when formatting from a G4 system... It's the little things that get ya.
So, quick checklist of things to do:
Format Mini's drive as GUID
Download latest MySQL 5, MovableType, Courier-IMAP, Courier AuthLib, Postfix, PCRE, PHP, Cyrus SASL, policyd
Shut down all services
Clone drive from G4 to Mac Mini
Boot 10.5 Installer
Install MySQL, PHP (built for 10.4.x, will upgrade to 10.5 versions when available)
Build/Install PCRE, Cyrus SASL, Courier AuthLib, Courier IMAP, then Postfix (order probably important)
Keep fingers crossed
Hopefully I haven't forgotten anything that's a dependency, if so, I'm sure I'll find out about it.
I'll probably try for a dry run this weekend, and see what happens.