What are your elec rates? Payback for what we pay in my area ($.16) does work out. I know a few guys who are from Nebraska and if I recall correctly they are paying <.$04 though their local co op. At that price I'd agree it's not worth the money.
EasternPa, your contractor should be able to show you whether or not it is cost effective for your area. Is the proposed system water to water geo with hot / chilled water coils?
In Lincoln we are at .0565 for first 900 KWH and .0419 if over 900 KWH. There is a proposed 12% raise shortly.