I am not in law enforcement, but I have a number of former students who are in one way, shape or form. The answer to your question is going to vary according to the individual's experience, and there are any number of jobs in the broad category of law enforcement. To start, let's assume you are talking about everyday policing as a member of a municipal police force.
From what I hear, there are a number of intrinsic benefits to the job, which is why people endure the considerable downside to the career. The hours are long, which makes family life difficult and an understanding spouse and children essential. The pay is roughly equivalent to that of a public school teacher, or a little worse. Obviously, sometimes law enforcement officers are in harm's way, and everyday have to deal with the stress and anxiety of walking into the unknown with every shift. Police also have to deal every with some of society's most unsavory and unpleasant citizens, including drug addicts, prostitutes, domestic violence calls and drunks. This, along with everything else, often leads to job burnout in a relatively short period of time.