I've still got a few BeOS CDs somewhere, including a few Intel ones which are rather picky about graphics cards (in most cases you get slow, minging, 800x600x16 shades of grey) and (needless to say) don't run under VMware, and (I think) a PowerPC one that only runs on really old Power Macs. (I once ran it on a Umax Mac clone I had at Monash, which puts it in historical context.) It had a UNIX shell, and you could compile text-based GNU apps, but because of its revolutionary design, it wasn't anything like any OS in popular use, and hence had only a handful of uninspiring shareware apps. All in all, nice swing, no follow-through.
Now the question is whether Palm will attempt to shoehorn BeOS onto their palmtops; if they do, it could be awkward (witness Microsoft's ill-fated forays into PDAs. OTOH, PalmOS could get rather cramped and unscalable, much like the old MacOS (which it resembles to an extent).