First, Thanks to Oldman for the websites. They gave me a better idea of the kinds of jobs out there in public health.
Looking at the jobs offered and the qualifications, I don't think a MPH would be worth it for me. (What got me thinking about it was that I was sent an invitation to apply to a program, so I haven't been seriously thinking about it.) Skimming over the job postings, very few of them were looking for a MPH. I'm sure it would help when applying for those jobs, but the required or preferred degrees were mostly PhD or MD, with experience. A lot of the positions were academic, which I have an interest in, but didn't list a MPH as a requirement. So I've decided not to tack on that extra year to med school. I don't know what your goals are Dr.Quack, but those websites might help you make a decision too.