Sorry for the delay. I've finally finished a move, load of other work I had to do and setting-up a new office where I can continue development more efficiently. Work has already restarted and I'm committed to get this project finished before the end of the year.
A small update to the source was published on GitHub last week to fix an expired certificate (https://github.com/emlid/Navio-SDK-Windows-IoT/issues/14) so it's usable again now.
I've also adjusted and 3D printed the Navio 2 case from the forums here to work with Navio+, Raspberry Pi 2 and 3 interchangeably: http://www.thingiverse.com/thing:1780041
I now have the 3D printed parts I need to build identical drones with each Navio model for proper Windows IoT testing, proof of concept and cross-platform benchmarks. This reference build will be documented with photos and published soon.
Some people have already implemented a couple of the remaining chips which were possible (don't have issues described below) in branches or private code, namely IMU and GPS. Just be aware as indicated in the documentation, that until the core SDK is finished major changes will occur. Currently major refactoring is underway to support new hardware. The goal here is to produce a consistent, tested, reliable and easy to use framework rather than quick gains with errors.
The main issues are to do with real Windows IoT hardware compatibility which may prevent a feature complete version from ever being implemented, e.g. access to the second SPI bus, protocols and firmware for the new coprocessor in Navio 2, lack of buffered PWM input drivers for Navio/Plus.
With Navio+ we could live without RC input in a worst case scenario, but in Navio 2 it appears both the RC input and PWM output are hidden behind the new coprocessor. A drone/robotic solution without PWM output is pretty useless, so a proper solution must be found.
Regardless, I'll push support for IMU and GPS forwards in my priorities and get the official branch updated soon. You'll also see some standard interfaces appear which will help avoid so many code changes later.