Vantaggi
The main pro is job security. Even with cuts throughout the Federal government, if you earn even a bit of seniority it's very hard to lose your job. In addition, you can end up working with some pretty cool people and building camaraderie in your assigned area.
Svantaggi
You never know what you're going to get for job environment. Each airport is different in how they run things, and even each assigned station may change. Sometimes you have a regular assignment with a good supervisor (like my first airport), other times you rotate your assignment every day and have micromanaging, abusive supervisors (like my second). It's a turkey shoot and just hope you get something cool... otherwise, you may be stuck doing heavy labor for anal-retentive jerks.