Well, I don't know if I'd say it was an "heir apparent" to anything in particular, but I think BeOS was promising. You're looking back at it like an engineer, which is fair; I'm looking back at it as, well, a user, someone who ran it full-time for nearly two years. Sure, I ran into things it couldn't do, but most of the time I was kept enchanted by all the things it could already do.
At the time it was being worked on its main competitors were Windows 95/98 and (pre-Unixification) Mac OS; multiuser capability just wasn't that important. If development had continued, I don't think it would have been out of the question for a future version to include multiuser support. In any case, I really do wish we'd been able to see where BeOS might have been in 2009 if things had gone differently.
At the time it was being worked on its main competitors were Windows 95/98 and (pre-Unixification) Mac OS; multiuser capability just wasn't that important. If development had continued, I don't think it would have been out of the question for a future version to include multiuser support. In any case, I really do wish we'd been able to see where BeOS might have been in 2009 if things had gone differently.