Why you should try it: The WODs are essentially HIIT (high-intensity interval training) routines that involve short bursts of heart-pounding activity with rests in between. As you've noticed while admiring your CrossFitting coworker's toned biceps, this gets results. But the real reason CrossFit has become so popular is that it simultaneously fosters a super-competitive yet super-supportive atmosphere. Everyone from the new mom to the out-of-shape CEO is encouraged to give every workout their all—even if that results in a little dry-heaving (vomiting in the box is relatively common).
Keep in mind: When pushing it to our limit, most of us tend to compromise form, which can lead to serious injuries. Look for box owners who are sticklers for good technique, and start with at least one introductory session.