The new cat in the block is Leopard. Here is my initial experience with it:
I did a clean install on a MacBook without problems, transferring all user info + applications from an old disk. I had to reinstall, however, because of Adobe. Leopard will let you install on a case-sensitive filesystem, so I decided to give it a try. However, Photoshop didn’t like that, so I had to do it again choosing the case-insensitive filesystem.
On a different MacBook, however, things didn’t go as smoothly. This time a simple automatic upgrade was performed. It turned out that if you have APE(Application Enhancer) installed, you will not have a problem free upgrade. I had to boot into single user mode, remove all APE frameworks and panels and reboot. That wasn’t the end though. Upon boot, the system couldn’t find any users! And it didn’t start the setup assistant, so I had to go to single user mode again, reset the root password, login as root via the GUI and add a regular user, than transfer the /Users/olduser to /Users/newuser. That fixed the problem, but it was not like “Start the upgrade process, go have a coffee and when you come back you will have a new Leopard running on you machine”. It was good for Angel that I have some knowledge on computers and I managed to do all the above, but I can imagine, that a lot of people will have to format their drives, erasing all their data forever(because they didn’t backup) and do a clean install of Leopard.