Geo-thermal Heating (and Cooling) Anyone Here Using It?

Geo-thermal heating (and cooling) anyone here using it? What is the good, the bad, and the ugly about it? I assume the heat exchanger or heat pump must be powered by electricity. Is the investment in Geothermal heating worth the payback?
If so, given our energy problems, seems this should be mandated on all new home construction that can accomodate a geothermal system.
Love to hear your opinions … preferably from those who own one or installs them ….