One of my customers made an excellent suggestion.  He suggested that I look into whether this board will power down the desktop supply from a linux command.  What a great suggestion!

It turns out that it was easy to implement.  Now, if you do 'poweroff' command from the linux shell or select shutdown from the UI, the Mini ATX PSU will power down the desktop power after twenty seconds.  Why twenty seconds?  Because, Mini ATX PSU monitors the 'boot ok' signal coming from the Pi and if you reboot the Pi then it will just leave the power supply on.

This is really cool because now I can offer an Pi expansion board that will allow you to make your Pi into a desktop computer.

The Mini ATX PSU is for sale on Tindie.com.  Just look for the latest version, Rev. 1.1.1: 

https://www.tindie.com/products/tomtibbetts/piryte-mini-atx-psu-for-raspberry-pi/