I'm really curious about what might be behind Ken's experience with OS X as being "fragile."
I'm running a Dual 866 PowerMac G4, with a measly 256 MB of RAM. Back on Jaguar, I managed to hit an obscure bug which would reliably cause a kernel panic. (Haven't tested it on Panther since upgrading. Yet, despite panicking the machine multiple times in a row , I never experienced any "hard drive corruption or irreparable damage to system files." Just restarted, and it came back up fine.
This is a system with gobs of freeware/shareware/experimental-ware installed, some of it quite unstable by virtue of being alpha and beta software, but OS X itself has never had any major problems. I've done light C++ development work and video editing on it (half the hard drive has now been eaten by DV files), and still very few hiccups. It's actually gotten more reliable as I've slowly gone 10.2.3 -> 10.3.4
(And no, I don't really do any kind of regular maintenance. The occasional "repair permissions" if I happen to think about it, is the extent of it)
My XP machine at work, (a 1.8 GHz P4 with 1 GB of RAM) while usually pretty reliable, has a lot more problems than the Mac. Searching the hard drive for a file takes 5-10 min and grinds the entire system to a halt, whereas the Mac is done in about 10 seconds, for example.