Stomach-turning at times, yes. But also very, very eye-opening. The kind of thing you feel you have to watch just to say you had the guts to do so.
Plus, from a purely filmmaking perspective, it's a documentary that takes the rare position of no position. Usually the filmmakers are clearly on one side or another of an issue (like Religulous). But in Jesus Camp, they set out to simply show, not tell, and let the audience decide.
Many Pentecostals have raved about the film, saying it's a very accurate portrayal of their beliefs and practices. A 'thumbs-up' which makes the subject matter all the more horrifying.
As previous posters have suggested... watch it drunk or stoned. I saw it twice... once when it first came out and once again with my husband and mother. My mother is an ex christian whose beliefs used to be very similar to those portrayed in the movie. She cried and cried afterwards. I think it was such an eye opener for her to see it from somebody else's perspective. My husband was just angry.. he's never been a theist at any point in his life, so it was just one more reason not to become one.
If you can't download it, try renting it. I don't have a very low emotional tolerance.. I cry at everything.. so I can't watch it often. Buying it would just be suicide, lol.