I've done a lot of Crossfit. I also tried P90X in Kuwait, since they had a regular class. If you hit it with intensity, it is actually a very good workout. In my opinion, it hits isolation exercises too much, but it was a good change of pace. You will definitely get in good shape doing it as well, though. Since I was doing it as a change of pace, it was nice, but I think I would get tired of repeating the same 12 DVDs over and over.
IMO, the keys to a good program are change, intensity, and enjoyability. You have to keep changing up to keep your body adapting and improving. Intensity is important to success in any program. Most importantly, you have to enjoy it, or you will eventually fall off the wagon, no matter how good the program is--a mediocre program that you hit hare because you like it is better than a great one you stop after a couple of weeks.
For me, that program is Crossfit, though I add some more straight cardio a few days a week to keep me in good stead for the PFT. For others it may be something else. There are several programs catering to applied, or practical fitness nowadays.