Basically it takes 2 years for an Apple OS to become rock solid.
Sadly, just about the time it becomes rock solid and you actually want to upgrade to it and just USE, they abandon all support for it, leaving you the choice of upgrade or risk certain software packages no longer supporting it as time goes on. When I bought a Mac, I thought I was leaving the endless Windows software update cycles behind. It's really starting to feel like I didn't. Worse yet, Apple forces you to keep updating your hardware too in order to keep software current (e.g. there's nothing wrong with my 1st gen IPod Touch except that I can't even get even the most basic software apps for it since even an App that just says "Hello" requires at least iOS 4.0 anymore and of course you can't get 4.0 for older devices, not even just a 'basic' version of it to keep those basic little apps running. That sucks. I don't want to throw out perfectly good hardware for something small like that. So much for being 'green'.