I spent eight months teaching in France through TAPIF (Teaching Abroad Program in France). It was a challenging experience--I worked in a small town in the middle of no where--but one I wouldn't trade for anything.
Everyone who does this program will have a different experience. A lot of it depends on where you are placed--in a big city or a small town. It also depends a lot on if you are placed with other assistants or alone (as I was). At the beginning I was really anxious about living alone in this tiny town but it was a priceless experience, especially for developing my French. I lived with two French teachers--one of which was also new to town. My French improved dramatically over the eight months that I spent there. Another bonus of small town living is that it's cheap!! So I was able to take the generous time off (you only work 12 hours a week + there is an academic break of two weeks every six weeks) to travel and explore Europe.
Yes it was challenging. It could be hard to be alone. But I was able to do and see so much. I would definitely recommend this program, but advise prospective applicants that it's a growing experience and that it wouldn't be without certain challenges.