I leave in less than two months now (something like 55 days) for Maryland to begin plebe summer for the United States Naval Academy. After the summer of basic training, I will attend the school for four years (they own basically every summer after the first one as well) and, after graduation, be enlisted as an ensign or officer in the Navy or Marines respectively. Because the government pays for my schooling there (about a $350k scholarship), I have a five-year service commitment afterward in either the Marines or Navy - USNA lets grads go into either service.
Ever since I was a kid I was always interested in the military and everything to do with it: special forces, fighter planes, war history, etc. Fortunately for me, I got into the college and never really considered enlisting. That doesn't make it a bad option, however, as the military offers great government and retirement benefits, good housing (the definition of good depends on which service and where), a stable job, and decent pay - especially for officers.
I'd say go for it, but definitely think about it extensively beforehand. These are precious, precious years of your life that you will not be in control of, so only do it if you think that the experience will be "worth it", i.e. that it will prepare you for the rest of your life and give you valuable learning experience...which it most likely will. The military isn't for everybody, but if you think it's for you, then best of luck ;).