I attribute my success to having a computer science background from being a gigantic nerd my entire life (first code written was QBasic in 3rd grade and you KNOW I was at every lan party in high school) and luck (Had someone willing to hire me to maintain small fry websites for a year which helped my resume quite a bit although at a poopy salary).
Both my brother and I went this route after getting unrelated bachelors degrees from a large university. I think a lot of people don't become competent after these bootcamps because they just aren't technical enough to grasp the concepts at the pace they're introduced in class.
The people in my cohort have been fairly successful. Without checking I think about 50% of them have jobs as web developers now.