Billions of dollars. Windows Phone has been failing for years, and the same chorus has been saying "just a little bit more!" while Microsoft dumped billions and a large amount of goodwill into a clearly failed venture. They put more effort into it that the overwhelming bulk of businesses on the planet could ever imagine. There's a point where it's just a lot of good money and effort after a futile cause.

People's discussions about Windows Phone -- the invariable commentators who talk about how great it is -- is the sort of thing I'm incredibly wary about, having been misled by it before in this field. The people professing love for Windows Phone almost invariably spent very little time with it (and haven't dealt with the enormous number of flaws and gaps), or have a profound bias to like it regardless.

As a developer across a number of platforms, and with no affinity or vow of loyalty to any of the makers, I think it was a terrible platform that had tiny nuggets of promise, but never a compelling enough reward profile.