I considered upgrading to Tiger, suspecting that it might upgrade the CLI utilities to deal with resource forks and improve the Aqua/X11 integration.
I knew it wouldn't add the windowing system features I wanted.
I didn't care about the new features (Spotlight, uh... other stuff...?), as they would have little immediate effect on my productivity.
I decided it wasn't worth buying a once-a-year ticket on the upgrade train to gamble that eventually Mac OS X would allow me to work the way I want to work. Maybe that makes me a fool and a crank and a puppy-hating jerk, but I run into frustrations maybe once a week with Linux and ran into frustrations a couple of times an hour with Mac OS X. It just didn't make sense to me.