Mr. Vicente Ruiz, a Spanish advocate of the use of free software was interviewed here. Sure there is life after Microsoft, but it still will take time before we come to that. What everyone also in the open source community have to admit is that Windows is standardized type of operating system which everyone knows and can work on. Is it a "prison" like Ruiz commented, I doubt that and if it is, then Linux is worse than prison - at the time being.
My point is that Linux defenately has its place in the server market but has a long and hard road to be the dominant OS on desktops. We have to remember 99,9% of the users are not geeks, who can code or manipulate the OS to their liking. It is the oridinary John and Mary Smiths who we have to think about and as long as every Linux OS is different from each other it is hard to conquer the market.
It is not an excuse that the OS is free. It has to be much much more, for one the users have to be taken into consideration. Linux is a great and powerful community but it is oriented by technology. Usability and users is a negative must in Linux.