People don't give a crap if the file system is better unless they are using their system as a file server.
It's vastly more important for a system to be usable then better. Users using their applications are the #1 most important thing a OS has to well and everything else pales in comparison. Better 'usability' can come from better design, better familiarity, better compatibility, or a accident of history. Linux is more usable then Solaris for most people so most people are going to use Linux if they are required to make a choice. Linux does a lot of things terribly, but the massive work people put into it pays off in the end.
The 'Good Enough is better' mantra comes from people looking at software from a upside down perspective: Concentrating on technical differences first and user using applications second.