The most interesting part would be the fight such a law would set up between states and the federal government. Medical Marijuana still leaves us with a, "well, it's not okay, but we're letting them because they're sick." Full blow legalization jumps right to, "Well, I guess it must be okay, then!" which flies in the face of federal efforts to demonize the drug. Imagine the DEA raiding your local drugstore or farmers market, because they are acting legally within state law, but violating the federal law.
It's the kind of thing that can reignite the issue of states rights and possibly redefine what it means to be a state within our union. Legalizing cannabis would open a big fat can of worms, with possible benefits in all regions of politics that deal with personal and lower than the biggest dog autonomy.
The Rev