I have made it a few times. Takes about 20 minutes on a really low flame (after its molten). The parts on the bottom burn really easily though, so tilt the pan once in a while to check. The butter is about ready when it stops making the bubbling noise. It should be golden brown.
Make sure to get a good quality butter. Scoop off the floating particles with a spoon. You can use a coffee filter to get the best result getting rid of the remaining milk particles.
I use it as a bread butter.
You can also use the liquid ready made ghee into coconut bread batter to make it tastier and softer.