Pros
Great entry job out of college, good people to work with. You will get a clearance and learn the business of the military which is applicable to other defense industries. Decent pay in the beginning with good bumps, by the time you get to lvl 3-4 your raises will be minimal every year even with good ratings. 9/80 work schedule (can be a good or a bad thing) This means you get every other Friday off however you are expected to work 9 hours a day + commute time which depends on your situation.
Cons
Work/Life balance depends on the program you are working for. "Innovation" is scarce as most programs are built around a sea of GOTS/COTS - expect to be continuously fighting garbage that wasn't meant to work together as Software/Systems. Benefits (Health, etc) are diminishing / cost more every year as LM manages their own health exchange. Generally will not pay overtime unless your program is on fire (normally subject to 45hours+ before OT will be paid - not including the 'free 5 hours' to get to 45). This gets more interesting with 9/80 schedules + expected "All in" attitude. Current CEO (defaulted) seems to have something to prove in not a good way (opinion).