Another point to ponder is, will you be content as a nav forever? If not, then don't do it becuase this is what you are signing the bottom line as. My best friend did this in 1994 as a senior in college. He never got to make it over to the pilot side due to 9/11 and deployments. He hates the nav job and does other non-flying jobs to avoid the community. he is sticking in for the pension and then bolting. As for transitioning to pilot, the fat budget days are falling fast in the military and there will be less of everything to go around. I anticipate your chances to transition will only get harder. I see the big budget briefs on the Navy/Marine Corps side in flight school and we are cutting a lot. Good luck to you and your decision.