The OS is a commodity. Shouldn't be a "premium" item, in my opinion. Now, let's go over some of the benefits Linux brings to the table.
1 - POSIX. If you want to develop for POSIX, Linux supports this out of the box.
2 - Mature, peer-reviewed and stable.
3 - No cost. But, support is available, for free or paid. Since Linux is peer-reviewed and is GPL, support can be very high quality.
4 - Best alternate driver support, due to support by Vendors (IBM, Acer, Oracle, etc.). The Vendor support leads to people writing drivers due to demand. Driver are ALSO peer-reviewed, leading to higher quality.
5 - Number one platform for clusters and super-computing. Leads to best support for algorithmic GPU use. Easiest platform to use for applications in this space.
6 - Considered standard platform for virtualization base. As a result, Cloud Computing based primarily on Linux.
Now, if a "desktop user" doesn't need or desire Linux, or prefers Windows, my opinion is that she should not be forced into it. If the user CHOOSES a platform, she will make an effort to use that platform.
So, don't try to sell the use of Linux. Indeed, Linux as an OS doesn't really need these efforts (it will be no worse off than it is now).