Apple - Mac OS X - Family
My new machine came with Tiger. So far it's mostly a posterior pain. Old software has to be upgraded, the install is bigger, Spotlight insists on indexing peripheral drives it should ignore, I can't see how to constrain search to a path, and Quartz Extreme is still disabled and Retrospect has no Tiger support in their (orphaned post acquistion?) Windows based Mac backup (you can use the Retrospect/Mac client -- but that's not a licensed use and it's not supported).
There are a lot of nice touches, but I don't see any big advantage in Tiger for me over 10.3.9. Given a choice, I'd still choose LaunchBar over Spotlight, and I had to pay $10 for the new version of Launchbar after I upgraded!
With one exception. In 10.4.2 the 'Simple Finder' (managed user option -- Children) is very nice. It was broken badly in 10.0-10.3, so it's great to see it back. The Simple Finder now supports multiple 'windows' based on the number of icons in a folder, and there's an option (choose from menu) to break out to the full finder. So an administrator can now log in as a child, then configure the system as needed, then return to child!
The kid support is almost worth the upgrade.