I saw and replied to your post on the other board, but figured I'd reply here too if someone else is looking for information:
I was a 4-year HPSP all through school. In my opinion it was the best decision of my life. I went to USC so tuition was stupid expensive and I would have been so stressed about finanaces if I had to pay for it in loans. With HPSP I was able to focus completely on school, which helped a ton.
Now, I work at Ft. Bragg in North Carolina as a general dentist and I'm loving it. Work is fun, patients are the most thankful you will find, and I am able to run my operatory as a mini-practice. I have funds to buy whatever materials I want and can do whatever type of restoration I desire. If you get the opportunity to do an HPSP do it!!
I forgot to add, I'm working less hours than my classmates and getting paid well. Granted, that will shift in a few years, but by then my contract will be done with the Army and I can either stay in or get out and make more money.
If you have any questions feel free to PM me and I'll answer them the best that I can.