His back of the envelope calculation is that Linux is about 10,000 bugs away from being fully world-domination ready -- or about 50 man-years -- and some of those bugs are due to lack of support from device manufacturers.
After 10 years at Microsoft with less than "10 minutes with any Open Source code till I left Microsoft-which is actually very typical for MS employees.", this expat left Microsoft and spent a year using Linux (mostly Umbutu). It was a bit of a shock. To be precise, he "had an epiphany that Linux on the desktop is 99.999% ready to go. Linux is lean, stable, polished and extremely rich. All of the pieces needed for world domination on the desktop are there."