Pros
Large corporation with great industry status. Well respected by potential employers and average people. Premium rates for niche skills if you are willing to travel. Corporate locations typically have great facilities. Management is typically respectful of work/life balance if you demand it. Some really neat and important projects with great rates. Stocks are rockin!
Cons
Large corporation with many layers of management lacking real leadership qualities. No formal company-wide career advancement paths. If you want a serious raise you need to move jobs. Non-corporate work locations can be sketchy. Lockheed's business capture teams are fairly cutthroat, leaving workers to deal with the fallout on site. Program managers appear to be trained to walk all over anything in their way. Must be prepared to set and maintain boundaries. Many projects are fairly mundane and full of grumblers. No profit share, just 401k matching. They stopped pensions a few years ago. As someone else mentioned, annual gimme raise of 2-5% barely keeps up with healthcare increases.