Disclaimer: This is MY experience firsthand--I have only exp with the Navy--I cannot comment on GMO tours in the AF or Army (even though these branches are phasing out GMO tours).
As with msg boards, opinions and rumors run rampant--here is my PERSONAL experience...
With consideration to GMO tours...I personally have talked to several GMO's. 90% of them said they had a GREAT time during their GMO tour. While it is true that there is a chance to be sent to Afghanistan, this is not the rule. I have talked to MANY flight surgeons--they basically work 4 half days a week, have weekends off, and have the opportunity to get their pilot or helicoptor lisences. You do as much or as little medicine as you want. The only drawback is that FS need to be with his/her squadron wherever they are stationed at (for single men/women, they said they loved it).
There are also opportunities to do Undersea medicine, radiation medicine, or just primary care GMO tours (not everyone goes to Afghanistan--many peeps do clinic stuff in SD, Bethesda, Florida, Washington, etc).
Also, many GMO's said that they liked being able to take a break before residency.
doc makes a good point. If you go to USUHS, you will basically be devoting many years for military medicine (7 years for ms, then whatever is added on for doing residency, fellowship, etc.) It is a tough decision.
Monetarily, GMO's make around 80-90k a year--after only one year of internship. It's not that bad.
Voxel, I personally know of one radiologist (cmdr) that makes more than 130k a year (not 90k). The pay is significantly less than civilian radiologists are making, but it ain't a pittance either. Also, your comment about higher ranking officers telling a person to "drop and give me 20," is funny but baseless. There is a lot of camaraderie amongst medical officers--none of that goes on. There is a HUGE difference in being enlisted and being an officer (that stuff goes on a lot in the former, not the latter).
Also, I received a civilian def for Rads, and when I go into the Navy, my only payback will be FOUR years, at an attending level status. It will be a great time to hone my skills at either SD or Bethesda before I go into Academic or private practice.
johnM, if you are sure about wanting to practice military medicine--go to USUHS. If you don't know--apply for HPSP (4 vs. 7 year standard payback). If you are strictly deciding from a monetary standpoint--it all basically equals out in the end. I loved having a stipend during medschool, being able to guitlessly spend money, free books, medical instruments, etc.. I know that I won't make as much money initially early on in practice--but I don't have the medschool debt.
Hope this helps.