Pros
Foriegn travel - there are many places that I have been too that I never would have imagined myself traveling to. A sense of belonging - the Navy really is like a big family (sometimes a big dysfunctional family). Wherever you go, there are people you know and people who will immediately accept you as part of their group. Medical and Retirement - In uncertain financial times, it is hard to beat the retirement package and medical benefits. Work experience and training - you can certainly get some good work experience and learn new skills.
Cons
Working hours at sea can be long and difficult. Normally, working hours while in port aren't too bad, but underway the job just doesn't seem to stop. It is also sad to see that the folks at the top don't know anything more than the folks down at the bottom of the org chart. Sailors don't always have the tools and material they need to do the job, so that is frustrating.