Very Interesting work, with a lot of independence, security, and great pay.
Pros
There is a lot of security with being a federal government employee. You can't get fired because someone doesn't like the way you look, or decides to hire a nephew. I worked all types of criminal investigations, including white collar fraud, drug cases, burglaries, robberies and assaults. It is a law enforcement position, and you are expected to work 45 to 50 hours per week. The starting salary varies, but you will be making over $100k after 4 years. Great benefits and a pension. You are a federal agent with all the authority of the FBI or other agents.
Cons
Can be stressful. Depending on your assignment you may be on call some evenings and weekends and expected to respond. You will sometimes work in bad areas, executing search warrants, surveillance, and arresting people. You will sometimes be considered a postal employee for some benefits, which isn't always good.