Well, here is my small perspective about the Navy.
First: I'm an enlisted Nuclear Mechanic on the USS Nevada (missile submarine).
If you joined to become a nuclear officer, a commissioned submarine officer, they would pay you up to at least $20,000 sign on bonus. Now, don't get me wrong, there is good money in the submarine world but the officers work their ass off in the sub world.
We are very limited on space and so you would be in charge of many things as a new guy and still have to qualify (for officers, that takes two years). Think of qualifying as 2 extra years of full time school with a 40 hour work week... then expect only to sleep 3-4 hours a day, except drill days (3 days), field day (1 day), training days (2 days). So you will get one day you might get a full 6 hours, hopefully
That is the basic rundown at sea for submarine officers. Now, the kicker is: if you don't recommission yourself and say that you will come back to the sub force, you will be sent to Iraq, Afghanistan, or Cuba, or wherever the Military needs you. So either stay Navy or go to the sand. Pretty ****ty deal if you ask me.
Ok, another small aspect of the military: As a Junior officer O-3 and below, you cannot make decisions for yourself. The Commanding Officers (captain of a submarine) are getting more and more micromanaging of crews as time passes. The focus is being shifted from common sense to blindly following orders and not using your mind. Be wary of the military, it seems that is the case always. "Do what your told, do what the PROCEDURE says, don't mess it up."
The only reason you should join the military is:
1.) You want to serve your country. That is a pride thing and no one should be able to argue that from you.
2.) You want a degree for... "free". Depending on your path it may cost something. Remember though: there is no such thing as a free lunch.
There are many other reasons but never join the military for the JOB. The job is horrible, underpaid, and highly stressful. Remember that you are getting paid salary: that means 24 hours a day pay. That means as long as you are awake you can be worked and trust me, I've stayed up manning battle stations for training for 49 hours straight operating a nuclear reactor. They will use you because you are free contracted labor.
Would I do it again: yes, I need the college money, and it is going to jump start me as far as experience, but would I stay for 20 years: no.
As of this writing: I have 496 days left in the Navy! Cannot wait to get a degree in Mechanical Engineering.