I replaced the Windows IoT with a Android TV build.
First thing of note, the 800x480x60 display I was using does not work. The experimental OpenGLES for Video Core 4 only outputs at 1920x1080x60.
As well ADB USB does not work. You must use ADB connect to manually install APK files for testing.
USB and Bluetooth controllers also did not work. So keyboard input was used for testing.
Again I uses Unity Technologies PreviewR201 project to test the Rpi3.
When first loading you get graphical errors which are soon replaced. The new 5.5.0b4 splash screen runs great. And the project loaded to start screen.
The project ran at 1920x1080p vsync ON with 30fps. And did so very smoothly.
Using screen.setresolution caused to color palettes to be malformed. So native resolution was only supported.
setting screen resolutions yielded
1920x1080x60 > FPS 30
800x480x60 > FPS 45-53, (color palettes issues)
400x240x60 > FPS 56-60, (color palettes issues)
The increased support for rendering does show promise as it provides much higher abilities then Windows IoT. The Video Core 4 GPU on chip only supports OpenGLES and not DirectX. Since UWP apps only support DirectX API, this causes a missive loss in abilities for Windows IoT on Raspberry Pi.