New versions may come out, but my point is you don't necessarily have to buy it. Sometimes an OS is necessary to run new hardware, but if you are keeping your existing machine, check reviewers to see if the upgrade is necessary for you. Being on the bleeding edge is not always the best course of action. I waited to upgrade to version 10 until they were in 10.2. The first iteration was really a growing stage for Apple. My jump from 10.3 to 10.4 only happened when I purchased new hardware. My jump to 10.5 happened because I had purchased two new machines for our home and I wanted all the computers to be using the same OS for integration and consistency. The stand alone powermac still uses 10.3
So... there has always been a reason for the upgrade and not just to have the latest and greatest.