Tuesday I will bring in a Raspberry Pi 2 running Windows 10 IoT Core.
Spoiler - it's not what you might think.
No UI :-( It's a platform to run programs compiled by Visual Studio 15.
Lots of stuff is not working yet, like USB WiFi.
But it's a start...
SPI, I2C and GPIO are working okay.
You need Windows 10 Preview running on your desktop to prep the SD card. Contrary to what Microsoft says, you can run it as a VM, but you need VMWare Workstation 11. USB SD adapters are not recognized by Windows 10 under Workstation 10 (or earlier).