I've had a geothermal heatpump for almost 10 years. My parents for even longer. They are great, especially in harsh heating climates. We live near Pittsburgh, and they have proved quite affordable. Local contractors have really just started installing them...I had to really look around to find an installer. Most HVAC guys don't want to have to mess with a well-drilling sub and a maybe a backhoe sub to trench from the wells to the house. It is a lot more work, compared to an air-source unit...and far messier! Install an air-source unit, you will get a few holes in your foundation for coolant lines and power to the compressor unit...and then the normal ductwork, air handler inside and the air-source unit sitting outside on a drop-down concrete pad. If the ductwork is in place, it is a 1-2 day job.
With geothermal, (if it is done right) you will have a dozen or more holes in your foundation for the in/out of the loops from each well into a manifold in the basement. You WANT that manifold in case one of the wells dies. You will have trenches from the foundation to the wells...and the wells need to be 10-15 feet apart, so some significant part of your yard will look like hell. Mine took about two weeks to complete because the well driller broke down on the fourth well. And the backhoe operator came *this* close to putting the bucket through my foundation wall. It is a monstrous headache to do a retrofit install, but for new construction, it would be a bit easier. In any case, the cost for the loop install can be a back-breaker. The geothermal units themselves are IMO overpriced too, due to lower production volumes.