Pros
The Bureau's mission is, hands down, one of the best in the nation. Motivated, disciplined, dedicated colleagues. Excellent resume bullet. They pay for your clearance. Excellent work/life balance, outside of the Special Agent career track.
Cons
Extremely limited mobility outside of the Special Agent career track, oftentimes superiors must retire in order to advance. Constantly changing policies (i.e. to go on a TDY, must be in position for one year, then two years, then not outside of your division, etc.) Absurd hostility to external training opportunities that would not infringe on workday nor cost the Bureau any money! Senior management in constant flux, frequently leaving for better opportunities in private sector. Atrociously behind the times in terms of technology. "Old School" mentality not uncommon, i.e. sexism, racism, favoritism Virtually all positions that aren't broad canvasses posted on usajobs.gov are posted with a specific candidate in mind, internal networking is the only way to identify new opportunities and is also, strictly speaking, not allowed.