I'm an ROTC cadet and have been looking into doing HPSP for quite some time, and have correspondingly done a lot of research into the subject. From what I have gathered from asking AMEDD recruiters (and the OIC of a recruiting region), currently almost all PGY-1 pulled into active duty service are in the Navy. Residency slots are competitive just like in the civilian sector, but certain fields are extremely difficult to get into (primarily specialties not in high demand for a demographic majority of young adult males). Keep in mind the service commitment as it can get convoluted when considering various training combinations (i.e. fellowships plus residencies). If you attend medical school on the HPSP scholarship, you will owe 4 years (amount of time attending medical school) or the amount of time spent in residency, whichever is more. You can only pay back your time commitment to the Army after you complete your residency training. Lastly, if you attend the Uniformed Services University of the Health Sciences you will owe 7 years instead of 4 because while attending school you will be earning active duty 2LT pay.