no scientific opinion here either, strictly personal.
The videos that I have seen of Crossfit did not look very complimentary but I have no doubt that it can be done safely if people are well-prepared for the exercises they are about to undertake. (But, frankly, I can say the same for many other forms of exercise in which proper form is not observed. Even yoga classes have been known to produce injuries).
It is another way to get fit (or get hurt).