@Truck BeOS was my first *nix-like OS. It introduced me to Posix and made me ditch Windows later. So, naturally, I love Haiku. Fond memories.
Popular is important, though. Because why? Because software. Right now, on the desktop market, we have a giant-ass system that almost makes a point out of not following the standards and being incompatible with anything else. And it, somehow, has all the software. And therefore, all the users. Which also means all the developers. Which means all the software. I see this as a giant problem. We need to do away with it somehow.
Seriously, I don't have as much of an issue with MacOS as I have with Windows.