Ah, I have a wife and wonderful baby too! The 45 days a year for the first two years are served "while you're at school." So, you pick 45 days a year to get a paycheck and that's that. The second two years, you work with LMU to let you do a rotation at a military hospital rather than one in the standard rotations. YOU STILL GET YOUR VACATION! So, say you find that you would like to do another internal medicine rotation (or whatever) or replace one on our schedule with one at Walter Reed or Bethesda, San Diego, Hawaii, etc.
In regards to having "more control over your residency" I find the opposite to be true. (Please, I don't want to start a DO vs. MD battle here!) All of the residencies in the military are allopathic and you have a great shot at getting what you want. I could write a few pages about how the military match works differently than the civilian MD, or DO matches, but its a good system.
Perhaps, I can get anyone interested in HPSP together during orientation. While I'm finishing up active duty, I'm doing a temporary duty working for the the Admiral in charge of HPSP and the Bureau of Medicine in DC, so I'll have a broad picture of what's going on when I show up at DCOM (I say this not to brag, but to imply that I have a pretty good idea with what HPSP is all about).
I welcome any more questions. I don't get paid for recruiting, but I've had a blast in the navy and I think it's a great option!