Here's my $0.02:
1) AmigaOS as we know it, be it 2.04 on an 68000 or 3.9 on a PPC will never be as stable as one of Microsoft's 32-bit OSes if you measure pure uptime.
2) The only MS OS I've never experienced any trouble with is NT4. I still use this at home and I must say it's impressive. However -- if anything DOES go wrong (and I have countless examples; registry keys not working although they are set up correctly, networks screwing up, files that isn't updated in the web server although you delete the old file and replace it with a new one and so on) you have very small possibilities to check for errors.
The sysadmins at my work have tried to fix a small but annoying error on my Win2k box for half a year now and the only thing they can say is "well, we'd better re-install it". In Linux and AmigaOS, when something goes wrong, you know where to start looking and probably the error is fixed in no-time. There's a good reason why AmigaOS has libs, c, devs, s, fonts and so on and not just 40 megs of (undocumented) system software placed in dh0:amigaos/
3) Microsoft won the office market, Amiga won the hobbyist market. Then Commodore went bankrupt and Linux took Amiga's place as a hobbyist OS (since this discussion isn't about servers, let's not go there
). Still, Amiga is the one computer that can fuel my creativity and impress me.
This is how I see it: All operating systems suck. AmigaOS just sucks less.