Think there are 2 different main types of Ground Source Heat pumps, the one where the collector is close to surface(on a large area) and the second one were a hole is drilled to 100-150 m depth and the collector is lowered down there. Believe the later one is the more efficient one and very popular in Scandinavia. Downside is high initial costs and You also need to have water based heating system(floor or radiator heating) increasing the costs further. What I heard from my neighbours, its working well, despite the fact that further heating (electricity) is need during coldest time of the year. In Sweden think the number of installed system is more than 250 000 units, can't be all crap. But You need to hit the hard stuff to get it working well, so it depends on the soil down under.
The newest trend is to build houses isolated so well that they are based on passive heating(technically no external heat source regularly in use, but isolation is huge). But moisture might be a issue(?) time will tell.
I have neither, as this area is connected to district heating(cooling water from a power plant some 20 km from here) so we just have e heat exchanger in the garage and piping from there to the house. That's also why we have floor heating in the garage
that would be normally considered insane....