I used to smoke when I was a teenager, and have to say that the medical benefits are somewhat of a mute point. Most of the benefits can be derived from other sources, and usually ones that have a lesser chance of side-effects. Those that can't are MS, and Cancer; which I can attest that if it is legalized for medicinal purposes it will be a controlled substance, thus still not available for recreational use. [Sorry guys...]
Fact be I used a lot of drugs when I was teenager, and I have to say that I don't support any of them. All, including Nicotine, have an affect on coordination and reaction time. Cigarettes are kept legal, if demonised, for the fact that Nicotine isn't classified as a drug. It's considered a 'smooth relaxant', and while it does still go under aphrodisiacs, it's still no more controlled than most ingested sensitivity enhancements in the fact that you have to be of age to purchase them.
Now that I clarified a few things I'll bring up another aspect. To legalize it for recreational use would mean we would have to install another agency to control it, or take out those specifically designed to target offenders. This can't go to the ATF, for they already have their hands full with what is already on their plate. Furthering this is the money that would have to be spent taxing, and controlling it which wouldn't even begin to come back to the government until 30 years after legalization.
America cannot afford to legalize cannabis, at-least not in their current state. This speech is not to say that I am against legalization, I'm just stating the facts. Even if the people in charge will agree, the problems it will incur afterward will keep their hands at bay. I would actually like to see it legalized on the same level as alcohol, not for personal use, but merely as a means to cut down the drug dealers sources of income. I've seen too many scathe by on the harm of others through drugs in general.