Pros
Promotion is almost guaranteed as long as you are in good physical shape, stay out of trouble, show respect, and do your job. Great job security - American will always need a military. Lots of prestige. Great team unit. Pay is on the low side of decent, but as long as you take advantage of the benefits that the Marine Corps offers, you can easily save a lot of your take-home pay.
Cons
Some of the higher ranks abuse their power and don't treat the lower ranks with proper fairness and respect. If you have any kind of problem with authority you probably won't do well. Long hours depending upon the unit you are with (aka your specific job title). Sometimes there is too much travel (back-to-back tours of Iraq). However, every job is unique within the Marine Corps so it's hard to make a blanket statement about the downsides.
