Well I have to say that Leopard is by far the worst experience I've ever had with any Mac OS/X upgrade. My systems (both PPC/G4) are slower and my laptop has hung four times now in the last two weeks -- twice in the last 24 hours. It's absolutely unusable as far as I can tell. I will almost certainly buy future Apple products but this is a huge black eye for the company as far as I'm concerned. What a disappointment. One of the things I've come to value most about Apple -- it's products "just work" -- has been significantly eroded. Apple, stop everything else you're doing and fix this mess.
Casey
Ive got the update both installed on my SR Macbook and my G4 with a Gigdesigns 1.8 from the disks that came with the macbook. (temporary measure, I've since bought a legal copy of Leopard)
There was a bit of a hiccup, though, on the G4. At first, the Mac wouldn't start after doing an upgrade. It'd give me the tone, and then boop, back off it'd go. Even single-user mode would fail. It'd start shooting text, and after it said USBsomething, it'd shut off. Took out the USB card, and the USBsomething message wasn't any longer the last one shown, so there's some driver loaded right after the USB driver that's the culprit but I've not yet dug in. Don't need to.
Next, I told it to install on the external firewire drive, instead. This time, it was successful -- the computer would boot off the external, and all was fine until I did a system update and installed some of the iLife apps via pacifist. At that point, I was back to square one with one very important difference, however, and that is I'd migrated all files from the internal 120GB (Sawtooth+Radeon 8500). What this meant is that I could go ahead and wipe the internal as often as I wanted to reinstall in case this problem persists, all my data remains on the external.
Whatever happened, though, the Leopard install onto the blank disk has been just fine, and with Time machine making regular backups, I'm in pretty good shape in the what I hope is the unlikely event I'll be unable to restore from Time Machine, and even if I can't, I can always restore Time machine onto another external disk (I'll buy it if I have to) and then re-migrate. I'm pretty safe now.
Leopard hasn't given me any other issues and I think it's rather a nice change; Tiger was great, Leopard is better.