if you're really sure that you want to go into medicine, then one of these medical programs can be really great. it's competitive to get in one of them from hs (e.g., the people who end up at these programs often are also accepted to many top-tier/ivy undergrads and even offered scholarship money), but keep in mind that admission to med school is also pretty tough (and getting tougher) because of the overwhelming numbers. at the very least, you have a sort of insurance... and since none of them is binding (i.e., if you tell them that you decide against med school, it's not like they can actually force you to attend), it's not a bad idea even if you change your mind later.
i came from one of these programs myself, though it's an 8-year track, and pretty much all of us that have moved into the med school phase are happy with the decision (no MCAT, no expensive app fees, no waiting to hear for a decision). if you are really considering it, then i'd suggest looking into the 7-year minimum ones... 6 years is much too short. you wouldn't have much of a life in the 2 years of undergrad, and med school is very stressful both personally and academically; i'm not sure that 2 years in college is able to prepare you with the right mindset.