Depends on your definition of better.
OS10 did a good amout of catching up with the .4 release.
By better, I mean usable, intuitive, accessible, and having excellent programs: basically, everything the end user needs. Even Microsoft's OS X offerings are excellent--of course, programs like MSN Messenger and IE have to compete with the likes of Adium and Safari, so that's not much of a surprise.
Linux has a way to go on that front. KDE and Gnome are complete jokes, and Linux itself is kind of a redundancy considering the existence of FreeBSD.
I would say that 10.4 is actually a step ahead, not a catch up. Vista will be a catch up with 10.4. Linux is usually playing "me too" with Windows. I'm just not seeing a better OS out there.