Anybody who remembers my posts from over a year ago when I had to work with OSX running on macs will know I had nothing but loathing for them.
That view, however, was from the perspective of a developer forced by an unrelenting mac fanatic boss to use a basic G4 eMac when the specific application was clearly best suited to an x86 running linux. Problems were encountered that were all but intractable under OSX 10.3 Server that just about any linux distribution you can think of would handle without problems.
For basic home users that don't have certain developer expectations "out of the box", OSX 10.4 on a Core Duo class mac is going to blow themn away. It's fast, has lots of snazzy eyecandy effects (for those that rate such things as important), robust and pretty much does everything you could want a home system to do without any remotely complicated setup required.