Ventajas
Generally stable job environment, there are the occasional layoff threats, but there have been few people laid off in my 10+ years there. Generally intelligent managers who have actually been successful technical workers before moving on to management. Highly ethical people. Only 40 hr weeks with flexible schedule. Salaried workers who work on the weekend or over 45 hours gets paid straight-time overtime (e.g., working 60 hours in a week gets you 55 hours of pay.) Alternatively you can take it as comp time and use it as vacation. 9/80 and 4/10 schedules available (Fridays off).
Desventajas
Slow, big company. Quota system for raises about 60% of people get the "Meets Expectations" rating, 30% a level higher, and only about 10% get the highest rating and raise. This quota will be shoved down your manager's throat, so if you're in a group of 10 people that have done the work of 30 and gotten the attention of executives because you did such a bang-up job on a project that made Lockheed Martin look great it doesn't matter. 6 of the 10 will still only get the average rating. Oh, and maybe a plaque for your wall. And maybe, just maybe a small bonus, a few hundred to a thousand dollars.