To the average Joe? That doesn' even know what a respondsive sleek and sexy OS is? Hmm... none? Ok, maybe booting time, and maybe the fact that it exposes the user to computing stuff that he would run away from if in a PC. Well I'm assuming MOS is like AOS, cuase I realy haven't used it. Same for A1, few advantages for the average Joe.
Hey, there is one BIG advantage. Not supporting the current PC market that is an ultrage to "real computing", it really kills any decent alternative that could exist, except Linux.
[EDIT] But then the average Joe is not an idealist, he buys the cheaper "more appeaing" stuff....