I do not think that Linux is dead on the desktop. If the desktop itself is dead, than that makes Linux all that much more viable as a desktop OS. Assuming that you are correct about people abandoning desktop and laptop computers; Which OS are they abandoning? I propose that most Linux users are Linux fans, and that Linux fans are not likely to abandon desktop computing. Therefor, assuming you're right about desktops; Windows' market share should steadily decrease while Linux's market share steadily increases, and overall computer usage steadily decreases. 

I also will say that Ubuntu was my first Linux distro, and that I left Windows to use Ubuntu. I know another guy of whom that is also true. I owned computers running windows for 11 years before I ever tried Linux. I have two other friends for whom I have built or bought computers, and installed (exclusively) Linux on. One is running Ubuntu, and one is running Mint Debian (a distro which was founded upon Ubuntu, but has switched it's core out for Debian). Thus my argument here is that Ubuntu has done a good deal in my personal experience to switch people away from windows. 

As far as your reasoning to migrate (and migrate our friends, etc...) from Ubuntu to Debian, I fully agree. Debian is very easy to use, modify and live with. It's only slightly harder than Ubuntu to install, though it's a good deal more complicated to (full) upgrade. I have been slowly migrating my own computers, and others' computers that I'm responsible for to Debian, or Debian based systems (like Mint and CrunchBang) for the past two years. I have been happier overall With Debian, and so have the people I administer computers for. I think that Debian as a desktop system is nearly perfect. Tools exclusive to Debian based systems like deborphan, localepurge and module-assistant only help to strengthen that opinion for me.

I don't think that I would agree that we should be helping to migrate people to smartphones. At lease not to what are currently defined as smartphones. I think we should encourage people to use Free software applications, and to save and store their data in Free and "open" formats. I think the core of the system is less important in that regard than the user level applications. I'd rather see a loved one using free software applications like Firefox, and Libre Office on a Windows machine than Closed source and proprietary software on Android. At least that way they could retain their own data. Having a Free kernel does not offer as many tangible benefits to the lay-user as Free applications do. (Having both Free is obviously superior to either option)

If there were a Free smartphone OS that was as ready for the average user as Gnome, KDE, LXDE or XFCE (and perhaps others) are on the desktop, I'd probably concur if not agree with you on that point. As it stands I can not.

Thank you for contributing such an accessible and thought provoking show. While I disagree with several of your supporting points, I enjoyed hearing your whole show, and I agree with your overall point of questioning, if not abandoning Ubuntu. It was a good, and fun episode. I hope you decide to do more in the future.

Sorry to write a book in response, but like I said, it was thought provoking. :)

-pokey