home heating: geothermal, solar, other?

HI!  I just found this site today, and this is my first post...

I read a greenopolis blog which mentions geothermal heating & cooling

http://greenopolis.com/myopolis/blogs/dberry-marketing/why-push-air

at a company named Earthlinked:   http://www.earthlinked.com/

Has anyone tried geothermal for heating & cooling of their home?  What has your experience with it been?  Does it really work?

The biggest energy pinch for me is heating my home in the winter.  Our heating is gas, forced air.  We replaced our unit with a high efficiency Trane a few years ago, but our gas bills are still very high.

How do I figure out what my savings would be, if I added geothermal heating to my home?  How much will I be helping the environment - is there a way to quantify that?

What about solar panels?  How do they compare to geothermal?  Do they gather & store as much energy? What about the energy and by-products it takes to produce, deliver, & install either of these two types of systems?  (i.e. other, hidden costs?)  Even given these other costs, would the numbers come out to a net savings or benefit?

 How do I get realistic calculations on what would both cut my fuel costs, and also be good for the environment? I live in the Philly area, so not as much sun as other parts of the country like Hawaii, Florida, or California, and often winters are pretty cold.

thank you!