I think the idea that Windows has never been closer to extinction is extremely shortsighted. Windows Phone market share got off to an extremely slow start because they were late to market and didn't anticipate the success of the iPhone but their market share is growing (more quickly in Germany and many other countries than in the United States, but it is growing here as well). In the meantime companies like Nokia are bringing devices like the Lumia 1020 to market with hardware like 41MP cameras, the likes of which are unheard of.
Microsoft certainly has more competition than they have ever faced before, and that is a good thing. As a result, Microsoft is learning to become more nimble, reorganizing itself into a software and services company, Ballmer is leaving along with Sinofsky, and as a result the future for Microsoft has probably never been brighter. Windows 8.1 is on the horizon (as a free update), the operating system is solid, quick to boot, leaner than Windows 7, fast, and fluid.
Windows continues to thrive in the enterprise and is growing in the cloud and that doesn't look to change any time soon. In the meantime Bing is slowly creeping up in market share as well.
In short, it is a mistake to just write off a company like Microsoft and decide to ignore a platform and insult your users. If grathan's opinion represents Beersmith and Beersmith has no interest in continuing to support the Windows platform than I clearly need to look elsewhere for my brewing software.
I will continue to monitor this and if there is no action to update Brewsmith for the Windows platform soon expect to see a kickstarter project to build some new software which is truly platform agnostic.