Squeek -- I got DQ'd for one episode of wheezing at age 15 -- I was 32 years old when I took the physical!!! I was able to get an exemption no problem. Your situation might be harder because you are currently using it. One of the the SDN members HPSP is a recruiter, he can probably tell you if it would be possible to get an exemption.
Dr. Will, there have been a ton of threads on the subject and despite my requests to the administrators, they have not set up a military medicine forum as of yet. I will give you the quick explination, but I'm happy to follow up more if you have specific questions.
HPSP is 2-4 year scholarship. The length of your scholarship is the length of you payback AFTER residency. If you do the scholarship you MUST apply to the military match and it is unlikely, but possible, that you could get a deferral into the civilian match. If your residency (not counting the internship year) is longer than your scholarship duration, you have to payback the length of your residency. For example a two year scholarship recipient matches in general surg (intership +4years residency), he must pay back 4 years instead of two.
My personal opinion is that it is a great deal if the military is something your are interested in. Financially, it is the best deal if you are going to a private school and/or you want to go into a low paying specialty.
Good luck
Ed