My .02... I've paid twice for OSX in a year and a half. First for OSX 10.0, which was unusable for most but for some reason I stuck with it and liked it (while gently cursing it every now and again). 10.1 was a free upgrade, and really needed to be. It stabilized the OS and made it a worthwhile product- I could actually be productive with it. There were still some performance issues, but it was as stable as any OS on any platform I ever used.
Now I've paid for 10.2, which doesn't strike me as a bug fix, but as a major release. 10.2 introduces significant changes to the OS, while no doubt fixing some extraneous bugs left over from 10.1.5. As others have pointed out, we'll probably go from 10.3->10.9 as future major upgrades, with dot upgrade bug fix releases inbetween. In a year and a half I've paid about $260, about what I paid for the upgrade from NT 3.51 to 4.0 many many years ago that introduced so much instability in my life so that I once had to work two days just to reinstall and repair my system so that I could use it. So to me, in the big picture, Apple is asking a reasonable amount for a good new release. And, as I did a great deal of professional work on 10.1.5, if it seems too much to anyone to upgrade then stick with 10.1.5, it's not, imho, an unstable product, it just isn't as good as 10.2. I know many people who never upgraded from OS8 to OS9... philz (not an Apple marketing rep, just a happy user)
