The people in this movie are zealots. Please don't judge the majority of Catholics as being like these guys. We're just regular Christians like everybody else.
The movie was well made, and some of the people in the movie recount some really touching stories. Some people talked about their first experiences with prayer. Others talked about how atheism just wasn't working for them. Many of these stories are even quite sweet.
Unfortunately, the Church often makes the mistake of trying to convince people by telling a completely one-sided story -- even when it's obvious to anyone with half a brain that what you're hearing is more than a little biased. This movie is like that, only more so.
Most of us Catholics don't necessarily agree with the Church's teachings on everything. Most of us Catholics are well aware that our Church is far from perfect. Probably only 10% of the Church is made up of Catholic fundamentalists -- but unfortunately, that 10% is by far the most vocal about their beliefs -- to the point of being "in your face" about how you need to be just like they are.
"Convinced" certainly isn't a bad movie. Just bear in mind that you're not getting a picture of what the Church is really like. You're only hearing from the most vocal and preachy 10%. And that's more than a little sad. The rest of us have other reasons why we like, or even love, our Church -- like the way Catholics care for poor folks more than most Protestants do. If you believed the movie, you'd think that we love the Church because of Apostolic Succession, which is ridiculous.