"We've seen this promissory note before," Miller said. "Java did this back in the '90s. But there's a lot of really custom work that will have to go into each platform."
Failing that "last mile" work, an app conceived for a smartphone will be seen as too simplistic for the desktop, while one with a desktop focus will be overwhelming and unusable on a smaller, touch-based screen.
Dawson was even more pessimistic about Microsoft's implied promise that universal apps will turn things around. In an analysis he published on his personal blog, Dawson argued that the universal app concept suffered from a fatal flow.
Microsoft's assertion, said Dawson, was that universal apps will let the millions of Windows PC developers easily port their apps to mobile, boosting the number of apps for Windows-powered smartphones and tablets and closing the so-called "app gap" between Microsoft's OS and those of Google's and Apple's.
"[But] the apps Windows Phone is missing simply don't exist as desktop apps on Windows," Dawson wrote. "Among the top 50 free iOS and Android apps, there is not one which is not on Windows Phone but exists as a desktop app on Windows."
His point? That it's the kind of mobile-first, even mobile-only apps that resonate with consumers that Microsoft most needs, and that desktop-focused developers are least likely to provide.
"I don't see universal apps helping Microsoft cross that chasm," said Dawson in an interview. "Either you already saw the logic in developing for Windows PCs, in which case you've likely already done a Windows Phone app, or you never have, in which case I don't see this changing things much, especially as it relates to increasing the number of apps on Windows Phone."
And other moves Microsoft has made seem to conflict with the universal app conceit, Dawson continued, ticking off the retreat from touch in Windows 10, as well as Microsoft's push into the low-priced part of the smartphone market, where users are less likely to pay for apps.
Windows 10's re-emphasis of traditional computing may make it even less of an attraction to app developers than was Windows 8, Dawson said. "By dialing back on some of the UI commonalties, Microsoft makes Windows 10 look more like Windows 7, but that means there's not going to be that visual commonality between apps [on different devices]. It may arguably perpetuate the core problem with Windows 8, [but] at the apps rather than the OS layer this time around," Dawson said.
So what's Microsoft to do? Or does the app issue even have a solution?
"Azure is becoming increasing important," said Miller of Microsoft's cloud-based platform. "It might not be the first choice for developers, but maybe Microsoft can own the back end for all their own platforms."
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