Pros
LM is a good place to start your career. Most of my co-workers were exceptionally talented, motivated and team oriented. I learned a lot from these folks and it was a good foundation for both the technical and business aspects of my career. The benefits are good and Management is supportive with regard to family and work/life issues.
Cons
Some Management teams are a real joy to work with. If you have the good fortune to be on one of these teams you will really feel good about working for LM. But as you go on to different projects be aware that all Management teams are not the same as some can have issues. When it does go bad you see Management conflicts of interest, ethical issues, glib disregard of employees professional recommendations, advice or warnings, permissiveness in allowing abusive managers to abuse without correction or consequences and ineffectual ethics investigation and enforcement. This is a big company and in all big companies making changes takes strong positive leadership. It does exist, but the company needs to do more to cultivate the environment where an employee "doing the right thing" is not abandoned to their own moral courage