I have been an OS X user since the beta release. I have an older iMac (333) with 256MB ram and I recently bought a G4 Powerbook (400) with 384 MB ram. I have been pleased with OS X since the official release, more pleased as it was revised and it matured.
As a recent (2 1/2 years only) Mac user and against the framework of extensive Windows and Unix experience, I can say that OS X won me over because of its stability, its Unix core, and Apple's artful GUI design.
I have never had trouble loading OS X , a fact best seen against my migration history: OS 8.6 -->OS 9-->OS 10 beta-->OS 10.xx-->OS 10.1. I did not create separate partitions. I just overwrote the old and kept going!
Yes, Classic has been too slow to load, no doubt about it. But that's a relatively minor inconvenience. Furthermore, I must add that my Office 98 apps have been fine against all these changes. This is important to me as I use Office 2000 at work and need to be able to move files around with no glitches between my Windows Office apps and my Mac Office apps.
Now why not ask me how much trouble I had loading NT 4.O -- both server and work station--when I needed to load those?
In fairness, Windows 2000 Professional is fairly easy to get up and running. And I would rate Win2000 Pro and OS X about the same in regards to ease of upgrading from their respective ancestors.
My only regret is that I must continue to use Office 98 in classic. I really like Office 98 and consider it a better suite than its Windows equivalent (I don't have a need for Access). And I think the Office for X is going to be too pricey. I will add here that I also just bought Appleworks 6.1, upgraded it for OS X and am absolutely delighted that it reads and saves Word and Excel files in Windows format. I don't have too much experience with the file conversions yet, but so far I am very pleased.
Complaints: only that Apple doesn't bundle with every new Mac and OS X CD a USB to serial conversion cable and the software to trick these USB machines into thinking they have serial com ports. I have not yet figured out how I am going to use my PowerBook to configure Cisco routers and switches via their console ports. But then again, that's not a problem most Mac users are faced with.