I've been following this thread since yesterday and the trend seems to be that archive and install is not always as effective as a clean install. What I mean be clean install is:
1. Back up everything
2. Erase HD with zeroes (voodoo really)
3. Install Leopard
4. Move everything back that you want/need from the backup.
This takes MUCH longer than archive and install, but this is the only way I ever upgrade to the newest OS.
Performance varies, but if you want to be sure you are getting the most from your machine, you'll want to do a clean install.
Unfortunately I already did the upgrade option yesterday, but I need to find a better way to run this smoothly - most issues in the article seemed to be related to installation issues and not performance issues.
Exactly the same thing happened to me doing an upgrade on my MacPro. I'm currently reinstalling 10.4 from a clone. I upgraded my MacBook without any problems.When I tried to upgrade, I had a big issue. Once the gray screen loaded up, it would get to the blue screen, and wouldn't go anymore. It simply would stop loading anything. I don't know if it was having conflict issues with my old Tiger installation or what, but I ended up having to do a fresh erase and install.