Microsoft last week said the next Windows 10 feature upgrade will be available for all users to download and install sometime in late May – the third straight postponement for Windows 10. The decision illustrates the strain under which Microsoft’s Windows-as-a-service model has been operating of late. What had been billed as a metronomic every-six-months release schedule for the feature-and-functionality upgrades has faltered, burdened by months-long delays.