What can it do with my lights that my IR543 and Harmony remote can't?
This add-on reacts on the state's of the XBMC player (which can be controlled by any remote,smartphone or keyboard)
For example:
One thing your Harmony remote can not do is Brighten the lights when the video ends.
In XBMC this is a player event, the add-on will react to that event and the lights will brighten, without you pushing a button.