At first I tried just copying across files. That's what I'd normally do when swapping machines, right? I had all my files backed up on an external HD, and files, including preferences and mail and address book and all those good things, were all I needed. Right? If only...
Instead, the upgrade software only does whole user accounts at a time. Not files. Accounts. And I can't just copy/paste for most system-related files (like preferences and mail) to work with the new system - it has to go through the migration process.
Now consider that I needed the new machines because I had a faulty old one. What if my old one had entirely died? Then I'd be out of luck, for "all" I had backed up was my data, not in user account format. And then, because it always is, it was more complicated than that, for my files in active use - mail, address book, current work files - were all on a third machine, a loaner. The loaner didn't have all my data - I didn't need it in active use, and anyways, there wasn't enough free harddrive space for ALL of it - but the loaner did have all the most current files.
So, three machines: old, loaner, new.
I migrated the old accounts over. I migrated my own account over from the loaner. Between my two main accounts, I had a whole functional one. But the problem is, of course, that as soon as I need to merge system-relevant files from two accounts, it creates a passel of permission repairs to tweak. The fixes aren't all the same either, unfortunately.
Pre-migration, during my first copy/paste attempts, zAngband was the only program which worked successfully on transfer. BBEdit, my favorite text editor, died. Mail only imported the directory structure, not the messages themselves.
Post migration, zAngband still worked and now BBEdit did too, to my relief. The system files weren't fully processed. Each time I've opened a new Apple program, its had to reprocess all its related files yet again. Fine.
But it's more complicated than that, because I had no idea how aggressively the Migration Assistant would move over applications from the other machines. The Migration Assistant moved over all the old applications, extra preference panels, and other installed featuers. All of them. Including those I have no right to. Now I don't intentionally pirate software - but Apple's making it might difficult for me right now. I don't know quite what software came with the new machine. I can check what's on the old machine and the loaner, but Migration Assistant won't always port over software if it already knows it has a more recent version. So if I have one copy - well, what of it? Did it come with the new machine? Was it just the most recent version off of one of the old machines? Is it mine at all, or does the software belong to the loaner laptop's owner?
When there are multiple copies of the same software, it's still the same problem. At least two of them are really, truly mine, but which? If it's registered, but without obvious named registrant, how do I know? If the software doesn't work on the current machine, that's easy. If I recognize the product and am certain I don't know it, then it's probably not mine at all - unless it came with the new machine, which, in some cases, it could have. (In some cases, I'm certain it didn't and can safely delete, thank goodness. And a named registrant which is neither me nor Apple makes it easy too.)
So no, not everything is functional yet. And there are bugs - there always are on installs. The most irritating one I've found thus far is that the machine doesn't automatically reconnect to the wireless network after sleep or reboot. (After reboot, it doesn't even remember the password for the network.) I'm working my way through possible fixes, but it's not resolved yet.
Oh, and zAngband? It was working fine until 11 pm last night. As of 1 am last night, I could no longer save files. It can create new files, but not modify old one. This isn't as helpful as one might wish... I lost my use of it somewhere in the process of clearing out irrelevant system preference panes which didn't belong to me and repairing my key chain.
My new machine is a work in progress still.