As a recent nuclear power Navy ROTC grad, I can tell you that your information is slightly off. All Navy ROTC students are obligated for 5 years of service from the day they commission. That contract is signed on the first day of sophomore year. If you choose to do something that involves extra training (like the nuclear pipeline which involves approximately 2 years of training due to delays in getting spots at schools), you are obligated for an extra year of service.
I recommend going the officer route through ROTC at Va Tech or Texas A&M (disclaimer, I went to Va Tech). I think that having the corps of cadets at a large civilian school offers the best of both worlds. You still get that military experience, but you also get the chance to get away from it occasionally to enjoy all the benefits of attending a large civilian institution. And Va Tech is a very service oriented school, especially their Corps. The school’s motto is Ut Prosim, “That I May Serve”.
The thing to take away from all this discussion is to KNOW exactly what you must do to fulfill your end of the contract you sign and know exactly what your particular service has obligated itself to do and what, if any, the penalties are for non-completion. (For example, you may have to repay any monies you received.)
Above all, talk to people about their experiences. Most of us agree our time in the service was well spent, but there's always thorns among the roses. It's important to recognize that too.