I clearly recognize a windows-user in you... why? because you seem to be used to major changes in every release. Well, Leopard has major changes, but not like the changes between eg xp and vista.
when you take a look at every non-windows system (solaris, linux, OSX) they are all following the 'release many, update often'-line of thinking, which means every few years, there is a major release, which has fixes every error of the previous version, and offers a bunch of new features. just look at ubuntu: every 6 months, there is a new version, and you have to download it, you can't upgrade you're previous OS toi the new version.
Windows on the other hand is always waiting like 4 to 5 years for a major release, and then they come up with a minor release (95(late 94) & 98(mid 97), 2000(early 2000) & XP(early 2002), Vista(2007) & Vienna/windows7(expected 2008-2009)). and in the time being between the major releases, the systems are constantly patched, so you end up with a completely f*cked up system(come on: 884 patches on my XP???). These patches slow down your system, and can't completely remove the problems, cause the problem is in the systems core. the patches merely get rid of the consequences of those problems.
Meanwhile, OSX is constantly adjusting itself from the core, and every 2-3 years, there is a major release, in which you get new major features (TM, spaces, hello?) and a slightly improved system architecture, which is different, but still very familiar to the previous one, while in winodws, you get a completely different system with every new release (Vista: no File, Edit, View anymore? XP: what was up with the start-menu? etcetc)
and last about the price: 150$ every 2-3 years is still less then 400$ every 5 years
