I participated in the program last year in autumn. Living with a host family and teaching at local schools was a great experience and a very unique one as well.
Patagonia is an extremely remote place and Coyhaique (the town where the Programme is located) is just about big enough to have everything you need. This is one of the aspects that made this experience so special - it's just a special place to be and the surrounding landscapes are gorgeous.
Another aspect that I loved was the cultural immersion, by living with a host family, being treated as one of their children and working at the schools you get the chance to really experience the culture and learn a great amount of Spanish. It took me just about a month to bump into people everywhere in the streets!
I also got to joint the national junior championship for Cueca (Chile's national dance) and travelled down to Punta Arenas and Tierra del Fuego because my younger host brother was champion of the region. That was a fascinating week!
Regarding the teaching, I was admittedly quite unlucky with the teacher I worked with. He had never worked with volunteers before and did not seem to want us there at all. However, you can always get support and the local representative is there to help you change school for example.
Finally I would also like to mention the absolutely amazing travel opportunities. If you're an outdoor fan, Patagonia is your place! We the volunteer group did a Roadtrip down south to Patagonia's most incredible landscapes. You get to walk on glaciers, do hikes with amazing views and experience the endless wideness. At times, we didn't see anything or anyone at all for hours - just a few Guanacos passing by.
Sooo I would definitely recommend this Programme to everyone who is looking for a unique experience, to learn a lot of Spanish (you should learn the very basics prior to arrival tho - everything else is a missed opportunity because you need the basic grammar!!!!!), experience real cultural immersion and loves the outdoors.