Let's not go too fast, however.
A couple observations: one of the as-yet unresolved issues related to marijuana use relates to the pesky fat-soluble nature of THC, and all the things we don't really know about what it does over time. With alcohol, intoxication while driving is rather easy to determine/prove. But what about pot? Is Spiccoli safe to drive without six months (give or take) of abstinence?
The other (related): the side effect profile for pot is pretty grim, particularly at high usage levels. How long do you think it'll take people on the pro-legalization side to begin acknowledging this? Isn't that rather like asking active alcoholics to acknowledge the problematic consequences of their drinking?
Last, does a medical marijuana certificate work like a prescription? Does it afford legal protection in employment situations, ala the American with Disabilities Act? Or can employers still do their own regulatory thing, insisting their cab drivers, pilots, heavy equipment operators and train operators abstain from Cannabis, prescription or not?