Navy HPSP: Caveat emptor. Seriously.
First of all, you have good baseline stats that will open doors up to some top medical schools, assuming you don't botch an interview and you can write a believable AMCAS personal statement. I'm not trying to be too cynical or belittle your Nature publication...but to be totally honest, to the Navy, a publication is a publication is a publication, not matter if it was in Nature, Science, JAMA, or the Myanmar Journal of Toenail Fungus. All military residencies use a point system for applications, and two publications in any peer-reviewed journal will max you out for research. Not to say that you should not continue to pursue scholarly activities everywhere you go, but you should know that Navy Medicine, in general, does not value research very highly--it's not a priority. Serving the OPFOR is the top priority, followed by caring for Tricare beneficiaries (dependents and retirees).
I know several Infectious Disease specialists who seem to be relatively happy in their jobs. The Navy ID Fellowship is 3 years, one of which is spent earning an MPH. One of these guys works at one of the Navy Research Units (google this) and spent two tours in Peru at a research facility. Another is a Professor at USUHS. A third spends a great deal of time on a "lecture circuit" teaching a Tropical Medicine course at USUHS and for the GMOs and other physicians at the overseas Navy hospitals. They have helped with disaster relief operations (2011 Japanese Tsunami, 2004 Japanese Tsunami, Haiti, etc), but strictly in a military capacity. Aside from this, there are very few opportunities for international work. You cannot, for example, decide to set up a free clinic in Sub-Saharan Africa on a whim because your humanitarian juices may be flowing. The Navy will put you where it needs you. Just remember this.
I did HPSP, and it was a complicated decision made with few alternate options. Despite a good academic record and strong recommendations, I still did a GMO tour before finally matching into my specialty of choice. My graduating HPSP class also had the lowest recruitment rate, which meant zero deferments for residency.
That being said, I cannot say that I am unhappy. My residency program is very laid back. Unlike some other clinical services, my department is strictly physician-run. Our chairman does a good job advocating for us. Our Department Head still takes call every few weeks and stays clinically-oriented. We only have two nurses, and they are strictly clinical. Our Enlisted personnel are very good at their job, motivated, and help things run smoothly in the Department. Our program director is also very receptive to our wishes and complaints. I can't see myself being terribly unhappy in the future, since I tend to make the best of my situation (something reinforced as a GMO). The only major issue I can foresee is the fact that the military seriously undercompensates physicians in my specialty relative to the Civilian world. There are, however, moonlighting opportunities (shhhhh) which could even things out a bit. The other problem I foresee is the lack of funding for FTOS fellowship spots. Maybe this will change when I'm done with residency and I have a staff tour under my belt.
So back to your original question. Don't do HPSP. Get into the best medical school you can go. Pay for it with student loans. Figure out what you want to do with your life, specialty-wise. Match into that specialty and start your residency. Then decide if you still want to serve in the military. If so, do Navy FAP (essentially, the Navy will repay your loans if you serve for 4 years after residency...the plus side is that you will have done a residency of your choice without doing a GMO tour).
HPSP brings with it many variables of which you should be aware. Hope this helps.
Also, take everything your recruiter says to you with a grain of salt. They will ALWAYS be overoptimistic about everything, because it's their job to find warm bodies to fill a future billet.