Pros
There is a great deal of room for advancement, but you really have to make the most of it given the tools and resources given to you. Management is great and the assignments are great. Working in a large organization is great because there is funding available for training and for traveling for meetings or conferences. There are rotation programs where you can try out different positions within the company for 6 months to a year. It's a nice way to get out there and find your nitch. Once you've found a place that's right for you, the opportunities are limitless.
Cons
If you like the defense industry, then this is the place for you. If you are not into defense, but like space-related projects (like satellites and Research and Development work) then this place is also for you. If you don't like any of these things, you may not enjoy working for LM. Some of the downsides is that, like any normal business in this industry, there are a lot of old ways of doing things... so if it's not broke, don't fix it. This is very typical of LM at times. It's only when there is R&D work that new technology comes out to replace the old. Working for a large corporation could also have its downsides. Yes, there is a great deal of growth opportunity, but that just means you have to work that much harder to get yourself noticed. You also have to be careful with office politics. Not to mention, the work that you do is very much government oriented so it also sometimes means that things are really slow and then really fast. Sometimes programs could be cut just out of the blue. So, it's a tough industry but it is definately fun if you're into the hi-tech stuff.