I work in the electric utility industry and geothermal is definitely the way to go if you can afford the upfront costs. There are still federal tax credits that make it more affordable (30%). It should take about 6 years (at the most) for payback on a geothermal system. After that, all you do is save money every single month for the life of the system. They are extremely reliable and you will be shocked at the change in your electric bill.
I had someone tell me once that in 6 years, you're going to pay for one whether you buy it or not (in either the cost of the system or the savings in electricity)... why wouldn't you buy one?