In light of similar fanfare surrounding previous releases of 9x and 2k versions of Microsoft Windows, Apple can be seen to have a more generally functioning software product in OS X. Having used it extensively, and coming from a Unix background I can safely say that the amalgam of Unix and Mac OS is a general success.
Though some driver issues were present in the first release, the subsequent updates have sorted them out. For example, there was no solution for printing for those of us who had anything but the bleeding edge Epson printers. This problem was rectified with the Jaguar release, where CUPS printer architecture and gimpprint driver system were added to the OS.
All in all this new operating system hasn't done worse than many other operating systems.
While some of the cosmetic modifications rumoured to be introduced in the final version were not added ( for example the old-style apple menu, old-style finder ) the new GUI is faring well in the face of new and old users alike, as an intuitive and elegent interface, and appears to be gaining popularity with each new iteration/addition to the user experience. For example Panther added a shortcut sidebar to the standard Finder Window, from which I am now inseperable. And I have almost worn out my F9 key from using Exposé - I am led to believe that this is a common complaint among Panther users.