Hi CarpetShark. Sorry, only saw your comment now.
Well, I'm not sure what your knowledge level is, as far as programming goes. I will assume from your replies that you have some programming knowledge, my apologies if my assumption is incorrect.
BeOS was built for multiple-CPU computers. In fact, the first BeBox came with 2 processors. As you know, multiple-core processors is the future. The core of Windows was made for a single-processor, and although the NT kernel was greatly improved for multiple cpu's, it was not built for it. Point for Be.
BeOS was built IN C++ and has an OOP, C++ API. Windows and linux, again as you likely know, have a C, non-OOP core API. There are wrappers that make them seem OOP, but they are simply that, wrappers. Another point for Be.
The problem with Windows (and to some extent Linux) is that they're continuously adding on to an old, outdated core. This can especially be seen with Windows. The root of the Windows API goes all the way back to Windows 3.0.
If you've ever done programming, you likely know that every once in a while, revision upon revision upon revision just makes one big load of crap, and you have to start anew, learning from your mistakes in the past and getting a new system that incorporates functionality to do what you want (instead of having it patched on).
Windows never did this, and neither did Linux. Perhaps I should've rephrased to say the CORE of BeOS is years ahead of the Windows core.
As for the Be API, I used it myself, and it is anything but messy. I wont' argue with the limited point, but that's part of the beauty of it. It's not limited in the sense that you can't do what you need to do. It's limited in the sense that Be was a simple, new OS. It didn't have a gazillion API's that bloated your memory. But that's nothing that couldn't be expanded upon, if necessary.