my 2 cents:
in my experience it was a load of fun and I learned a ton. I definitely would do it over again. However, I'm not convinced it was really worth it considering my specific goals. For one, many of the interviews i've been to almost talk down to my choice. At one interview the first question I was asked was "So why the hell did you do things this way, why did you get a master's? Why not just apply out of undergrad?" He was super critical. Needless to say I was honest, I just wasn't ready or sure. My point was that I graduated college when I was 20 and that I just couldn't make a career choice for the rest of my life, yet. I needed to feel things out.
I'm waitlisted there.
On the other hand, if you are serious about a particular track in medical school, for example research and you want to apply MSTP, by all means, do the masters degree. I feel in the case of MSTP applicants, performing successfully with a research based MS degree can really make a great case for your continuing down this path.
Anyway these are my 2 cents. Probably not even worth 2 US cents. Maybe this is worth 2 Canadian pennies.