Pot heads never really bothered me, at least not as much as drunks. If prohibition for the public good (not the person's health) is the real issue, then cigarettes and alcohol should also be illegal. But they aren't, so you might as well let the pot heads have their day too and just sin tax the hell out of it like cigarettes.
The fact of the matter is they (the pot heads, not the random occasional user) are going to do it anyway, we have decades of evidence of this, but making it illegal just fills our jails with otherwise nonviolent people and forces them into "the system" (where felons can't get good jobs and end up resorting to crime) and it promotes actual bad guys (drug dealers) to procure the stuff and do their posturing and turf wars and whatever other BS that is an issue.
So the end result of legalization "should be" more coins in the coffers, a lot less expense in housing "criminals", less expense in welfare for ex-cons who can't get a job, and a need for less violent drug dealers. But it remains to be seen if the "should be" turns out to be true.