As a former Windows Embedded Standard expert and former embedded MVP, I watched the most recent episode of the IOT Show by Olivier Bloch on Channel 9 with quite some interest.

Seems like Yocto is filling the large gap, Windows Embedded Standard, as a configurable operating system for IOT devices, had left for Microsoft customers.
With access to source one certainly gains some flexibility, but in normal project life build times matter and the construction kit approach of WES is, even today, not easy to match.
However, it is great to see that there is a configurable OS solution out there, which is supported to some extent and with IOT Edge by Microsoft.
Containerization, somehow, made the underlying OS commodity, anyway.

In any case, I want to recommend the IOT Show as a great source of information on the newest development in Azure IOT as well as Microsoft IOT efforts! Olivier is a great host and his guests are explaining complex stuff the easy way.