I'm starting school this fall and I'll give my experience learning about it:
Obviously they pay all your fees and tution and give you $2000/month. You DO NOT get a 20k signing bonus like the MD/DO/DDS. Your specialty pay when you are out is $1200/year....yes $1200. So you will be making almost right on with base pay. A little perspective, my bro-in-law is an anesthesiology resident with the Army. When he finishes his residency and starts his pay back his pay will go up an extra $30,000/year for his specialty pay.
I called different recruiters and asked them when I can apply.
-Navy offers 4-years of scholarships. However, the 4-years only have 3-4 slots as of this year. I don't know how it goes for the 3,2, and 1 years.
-Army only does 3-years
-Air Force only does 2-years.
-Each branch has a minimum service repayment of 3-years.
I then got in touch with some current optometrists (others with experience may be able to verify what I'm saying, this is what I was told). Please correct anything erroneous.
-Most likely, you are going to be deployed more often in the Army. This have pretty good potential to be in combat zones.
-The Navy deployments, if you get one, are generally humanitarian style on the hospital ships and can range from a few weeks to 6 months.
-The Army has an 8 week OCS type training that has nothing to do with optometry; you don't have to do one of that length in the other branches.
-The Navy (and possibly by extension every other branch) is very political and cut-throat. You have to kiss a lot of butt to get ahead of the others since promotions (if you want to make a career out of it) and triangular (less and less positions at each rank).
As all have said and will say, do not go into the military just to pay for school. My Dad was a green beret and on and on in my family. I would've joined out of HS if my parents hadn't insisted I go to college (good call).
Hope that helps. Again, former military, please correct anything that is a little off.