I've never really had performance issues with Windows, for a mainstream OS (something my grandparents have no problem using), it's just fine. Yet, if you desire to get into the "nitty gritty" and tweak Windows around like AmigaOS, you can.
As I see it, AmigaOS is for nostalgics, and/or geeks who like to tinker with things. *Some* ideas may be implemented a bit more simply, but overall, Amigas/AmigaOS is far more difficult to setup and use efficiently. (Try building up an expanded A1200/OS 3.9 system from parts, it's *far* more arduous than, say, PPC Linux even. A Windows PC, from boxed parts to a fully tweaked XP install, can be fully operational in less than an hour... and probably by my 80 year-old grandfather.)
Subjectively, I have *fun* using Amigas/AmigaOS, but (like someone mentioned above) I simply don't see the point in comparison.
