I think of it in kind of the same vein as P90x. Its good to get you into things but I don't think its intended long term. I'm not saying P90x = CrossFit, I think CrossFit is a hell of a lot better but still not a stand alone program long term.
crossfit has been around 100's of years. these last 10, they did a great marketing job on the word "crossfit", but all it is, is taking a few exercises and doing them fast. call it circut training, crossfit, or whatever, its been around a very long time. in 1960 when i was 5, we would do allsorts of combined movements..one wasdo a set dumbell presses then run a lap of the gym, then repeat a few times.
hang on the still rings, the run over mats put up like hurdles. always combining a few exercises. do them fast..
all those "crossfit" movements were a fun way at the end of our specific gymnastic training to train a bit more in a fun way..
a great workout. makes you average at all exercises.
you want to be really good at something, you better specifically train for that sport or event..
I will say that the only real problem I have with it is that it recommends doing stupid things like olympic lifts or explosive plyos while under lots of fatigue.
I think what crossfit does is great for the average person. They advocate health, proper exercise selection, and exercise technique. The problem is that their audience is so huge now. I see so many crossfitters trying to olympic lift who clearly have no idea what they're doing. This is an easy way to injure yourself. A lot of people just aren't prepared from a technique, flexibility, and/or strength standpoint to do explosive movements properly.
You can't just give a person C&J's to do and let them go at it. Even if you tried to teach them proper form, they're likely going to have strength imbalances or mobility problems that prevent them from performing the lift with the form you just taught.