I see your appraisal as honest, but yet the potential is still there, If Linux could do with an OS what Firefox has done with the browser (far far superior to IE8) then it would be more used.
I don’t doubt the potential is there, it has been for years but again the user and developer base in the problem for Linux. There are too many Linux distributions out there, not one unified UI and an user base that looks down on those computer users who want something more simple.
Again, I love *nix in general and use it for my own purposes but you need to look at this question from the point of view from John Q. Public computer user.