So I got my new Raspberry Pi 3 and installed OpenElec on it.
All working very nice and fast (finally!) and my Harmony one was working out of the box.
One thing that annoyed me: Whenever I switch scene or poweroff my system, the raspberry also powers off.
Which means next time I want to use it, I have to find it and disconnect/connect the usb cable.
But you can disable the poweroff by creating a custom remote keymap.
The file is located in /storage/.kodi/userdata/keymaps/remote.xml
Put the following in there to disable poweroff:
This makes the power button call NOOP (NO OPeration).