Actually I'd be surprised to hear of anyone being jailed for mere use. Standard procedure around here is to issue a citation and pay a fine. It was the dealers and importers that anyone devoted any time to. I guess that's out the window too.
I was kinda unexpected that anyone would mount a campaign for this - it is such a low priority issue. And I doubt that the change will be noticeable.
Recent studies have shown that marijuana causes brain damage. This damage is worse the younger a person starts. You have to be a sadist to wish this drug on any society.
http://www.medicaldaily.com/articles/11417/20120809/marijuana-brain-damage-memory-learning-drug-habit-addiction.htm