Allen, OK, this is our experience with the Air Force scholarship:
My husband applied to medical school and was accepted. He immediately deferred a year from medical school in order to finish his bachelor's degree (yup, that's right, you don't have to have the degree to go!) and because I was due with our first child. He next decided to do the Air Force scholarship to pay for a family during the many years he knew he'd have no income. He applied in the late summer of the year he deferred (to get the scholarship for the following year). With these scholarships, you have to apply VERY early in order to be a "shoe-in" so to speak. What also helped him not have any difficulty was the fact that 1)he'd already been accepted (although it IS possible from what I've heard to apply for a military medical scholarship BEFORE acceptance to medical school contingent on acceptance to med school - but if I'm wrong someone please tell me!) and 2)his dad was an Air Force captain (pilot). Your prior military service is probably going to be a HUGE plus in getting a scholarship from a military branch.
OK, the rest of what I can tell you is from the perspective of the Air Force:
You are immediately commissioned as a 2nd Lt. in the reserves once you are officially given the scholarship. The contract you sign says that you will give one year of active duty service as a medical officer for every year the Air Force funds your medical education. Your active duty service commitment does not begin until after your residency is complete.
You will be required to apply for a military residency before you can go on to the civilian match during the fourth year of med school. Based on the Air Force's projected needs of specialists, you will be more or less likely to get a certain position. If there is a need for a certain specialty that is greater than the number of military residency spots for that specialty, then you MAY be one of the people allowed to go onto the civilian match process in the specialty you chose (and they hold you to that specialty - no switching because it is based on THEIR needs). My husband is one of the people who is doing a civilian residency. The same thing happens if and when you desire a fellowship.
As far as the "perks": You obviously have a greatly reduced (if it exists at all) debt on completion of medical school. You are paid as a reservist (in addition to your scholarship that pays for tuition/supplies) during medical school. You are (in the AF) automatically made a Captain once you achieve active duty status. IF you are going into family practice, internal medicine, peds, or another "general" specialty, the pay is actually quite competitive within the military to civilian salaries (plus you don't have the added expenses of setting up your own practice).
What are the "drawbacks"? You obviously lose a certain amount of control over your career choices. You cannot advance very well through the ranks (and thus pay scale) unless you take these inane military medical courses designed for NON-MEDICAL officers (ie these are courses YOU would be qualified to teach as a doctor rather than wasting your time taking them). If you go into a specialty such as radiology (my husband's), surgery, etc, you will be taking a HUGE paycut in the years of active duty service. (My husband will be making a half to a third what he could AVERAGE in the civilian world).
In the end, you have to weigh the pros and cons for your own situation. For some the military scholarship is perfect and a blessing. For others the military scholarship would be a very poor choice. For us, it has been an excellent choice to date - both financially, and, ironically, career-wise. In the end, the military will do what is in its best interest according to its projected medical needs. This means that you might have a unique arrangement that isn't the norm - such is what my husband has at the moment (I won't go into the details since it is a highly irregular arrangement and one that they may or may not repeat). What I have described, though, is the normal, expected path. One other thing I suggest: when you are arranging with the recruiter to apply for your scholarship ask to see the contract you will be required to sign - just to make sure you understand every bit of what will be required of you and what you will receive (but, I guess that is always a wise thing to do in every aspect of life!).
I know Wifty was also interested in similar information. Let me explain that I wasn't trying to ignore her post! I didn't respond on that thread since I had already answered her questions on another website and it would've been redundant for her!
I hope I answered your questions! If anyone has any additional queries I'll be happy to tackle those as well!
Jennifer