69Rcode Mach 1,
As a Major in the Marine Corps who started flying AV-8B Harriers in 1997, I will pass along my $.02. I was commissioned in the Marine Corps after graduating from the US Naval Academy in 1993. I had a guaranteed "aviation contract" upon commissioning. Pipeline selection (jets, helos, or props) takes place after the completion of Primary Flight Training and is dependant upon your flight grades in Primary Flight Training and the number of billets available that week. Specific platform selection (AV-8B, F/A-18, EA-6B) takes places upon "winging".
After flying over 1300 hours in the Harrier, I feel I am qualified to say it is the coolest job on the planet. I'm sure flying any pointy nosed attack or fighter aircraft would give you a similar experience. It is worth the years of hard work, dedication, and sacrifice required to be entrusted with such a machine. There is no way I could describe all of my experiences in this forum.
That being said let me expand on some of the good advice some of the other members have passed along. In the Marine Corps, you are a Marine first, then an officer, then a pilot. Once you are commissioned, there is no guarantee that you will actually end up in a cockpit (medical disqualifications, needs of the service, etc). You must be prepared for this possibility. In any service you will spend time away from home. In my experience, engineering degrees are really only necessary if you have aspirations of becoming a Military Test Pilot or possibly an Astronaut. Aviation is dangerous. Airplanes crash and pilots die on training missions. You must be prepared for that as well.
Unfortunately I have to leave for work so I will have to stop here. I will be back in a few days. Let me know if you have questions.
Semper Fi,
Waldo