A first-time computer buyer would not want a Pegasos, or an AmigaOne, like other people have said. The main attraction of the Pegasos at this point in time is to be in on the ground floor of something new, and this is only appealing to people who probably already have other computers to use, and can treat this as an extra.
Also, MorphOS1.3 or 1.4 is not for the new computer user, or even the old computer user if he/she isn't familiar with Amiga-like OSs, because it isn't complete yet, and because there aren't necessarily a lot of people in the neighborhood who can help out with the problems that come up. Even experienced Linux users don't find this a smooth process yet, but of course some people prefer to be the trailblazers, so that's where the market is right now.
As for more advanced users and applications, just what advantage the Pegasos might have over other hardware I think has yet to be articulated, really. At present, it's mainly appealing because it's a geek toy, and in fact that may be enough to get it to critical mass. A lot of people into other OSs have said good things about the Pegasos board, and Genesi is pushing this angle hard. There are also the other, non-PC products that Genesi makes, and it seems there are plans to integrate them in systems that will leverage the Pegasos's strengths.
If the cpu roadmap is followed the way Genesi is outlining it, this could also be the fastest-accelerating product evolution in personal computing (is that ad copy or what?!). So by next spring some time we could have a small, powerful board to play with (anyway, people with enough cash could). There's still the question of exactly what problem is this the solution for, but with a line that goes from G3 to PPC 970, there would be a lot more possibilities.
-- gary_c