Admittedly I haven't looked at the issue extensively (which I should, given how close Canada came to decriminalizing marijuana a few years ago), but I don't see the point of decriminalization versus legalization. I don't see why you would simply reduce punishments to fines and so on when it is equally or less harmful than alcohol. I am under the impression that alcohol is "legal," not "decriminalized," and I think pot should be treated the same way - don't do it on the street, don't do it and drive.
Decriminalization is good enough for me. How often do you get caught smoking pot? Almost never unless you are an idiot, now if you run zero risk of criminal record..and the punishment is an 80$ ticket why not risk it?
Also I think the problem with taxing it, is that it's too easy for people to plant their own on their balconies.