I have my doubts about Crossfit being a healthy long term proposition. From what I have seen only a few people keep it up long term. It seems more like a short term rush. Reminds me of people who get into running, then train for marathons, do one and then stop running because the effort is too much.
I don't think anyone is against CrossFit. The general concern is that many of their athletes lift weights with poor technique and eventually end up injured, which isn't healthier at all.