My wife would tell you it has been good on her end. I personally have been pretty unhappy as a military dentist, but from a family perspective doing the HPSP scholarship was an excellent decision. We went USAF so I can only speak to our experience with that:
The good, from family's point of view:
1. avoiding the crushing debt of dental school (hugely important)
2. 100% job security / a predictable salary to budget with
3. 100% medical coverage (we had our first child last year and never saw a single medical bill)
4. predictable weekly hours (though long) and duty schedule
5. little or no weekend work
6. very liberal amount of vacation time
The bad, again from family's point of view:
1. minimal control over where you will be assigned to live, and a definite possibility of being assigned to a fairly godforsaken part of the USA (although you're unlikely to be stationed overseas unless you ask to be)
2. long hours. My work week fluctuates around 60 hours, which is probably on the long end, but I doubt your husband will be able to stay on top of the endless paperwork in less than 50 hours a week
3. lower salary than civilian jobs / private practice... but HPSP tuition benefits more than make up for this at a private school.
Bottom line: doing HPSP was an unequivocal "win" for my family. The only real negative is lack of control over where in the USA you will live. Perhaps you are wondering if your husband will be suddenly involuntarily deployed to the Middle East or etc. Although not impossible, from what I have seen this is very unlikely for new/inexperienced dentists: deployments are actually hard to get and sought-after by experienced military dentists looking to advance their USAF careers... so deployment worries probably do not need to weigh on your decision much.
Hope it helps.