i took the GRE -- very easy compared to the MCAT. you don't have to study! it's basically like taking the SAT's over again.
as for whether or not getting an mph is "worth it". well, it really depends what you want to get out of it. i wouldn't suggest doing it if you're not truly interested in public health. i also wouldn't suggest doing it as a way to get into med school, but i know some people do that. why spend all that money when you could work and live in the real world instead? there are plenty of work experiences you can have that will expose you to the medical field more than getting an mph will. wouldn't it be nice to save up some money instead of going into more debt?! if you still plan to go to medical school i would only recommend getting the degree if you plan to use it. for example, if you want to go into research or hold a public health leadership position.