I bought a Powerbook G4 when Jaguar was the OS X flavor and Panther was right around the corner. Working where I do, I had plenty of friends that could get me a copy of Panther when it was released, but in order to do things the "legit" way, I called Apple to get my Panther CDs in the mail for like $9 shipping or something like that. When I install an OS I like to wipe the primary HD and install fresh, except that when I tried this, I found out the Panther CDs wouldn't install Panther without a copy of Jaguar on the HD - they were an "upgrade" copy. So, I ended up getting a copy of Panther from my buddy and installing off of that anyway.
Lesson from this? I guess it's this: the more DRM that software distributors put on their software, the more end-users are going to get frustrated and get on the road to pirated software.
Anyway, after that, I would never wait for an OS upgrade to get a new Mac. That's retarded.