Dr. Sanjay Gupta is a convert on the issue. I have flirted several times in the last decade with changing my position on marijuana. As one who doesn't deny using it in my youth, I think legalized recreational pot would be a devastating blow to the fabric of our society. I remember thinking I could function while high. Yes; some people think they can function while drunk. But you can spot someone who is drunk.
As for medicinal purposes, I've been undecided for a long time. I found very interesting his contention that there is no scientific evidence to classify cannabis as a schedule one substance. Changing that classification would change everything.