The only one of these that I know is Haiku (as an extension of BeOS). I was already a Mac user when Apple was flirting with purchasing Be, so I installed in on my PowerMac 9500 and took it for a test spin. I liked it, though I was too young and inexperienced (and this was pre-broadband) to really get a good feel for it. I think I switched back to MacOS within a day just because what else did I know to do with it.