As someone who works in the fitness industry, I'll say there are some really good basic concepts in Crossfit. However, with how some of the "boxes" are run and the workouts are conducted, there are some major safety and long term health concerns. There is an element in Crossfit that seems to push people to drive themselves past reasonable and safe physical limits during their workouts. There are also videos all over the internet of people doing exercises at Crossfit gyms that are just inherently dangerous and have minimal real world physical benefit. I do know a lot of people who train at Crossfit locations and are in great shape, so I'm not saying they don't get results, though. I also heard second hand that one of the local physical therapists tells people, "Crossfit sends me a ton of business." Take it for what it's worth.