You will find quite a bit of squabbling about this question on the military medicine forum. Two things that almost everybody there agrees on:
1. DO NOT enter the military if you're doing it ONLY for money and otherwise dislike the idea of being the military. You will be miserable.
2. The best way to find out whether you would like it is to find a military doc or two at a base near you. Talk with him/her, shadow if permitted.
There are resources online -- each service has an HPSP page, I don't have the addresses on me right now -- but you really can't get a feel for what the military's like from a webpage.