Let me just say that I've tried Linux (and other Unices), and have mostly used Windows, but I am (extremely) dissatisfied with both of them.
So I've read a bit on BeOS, and how the architecture of the system differed from other OS architectures, such as those of Windows or Linux/Unix, in its simplicity, modularity and functionality (not to mention that I've seen screenshots). That said, I want to try out Haiku once it comes out.