i dunno, i cant really decide whether it would be good or bad...
here's how i break it down:

good (for legalization):
- increases tax money, government needs it
- reduces number of drug dealers- less business for them
- less underrage smokers- kids who want to smoke are more likely to just wait until they can legally, and less people will become addicted early
- its not very hard to get now, so why not control it
- by going into the business, the government might have an easier time tracking illegal drug sales

bad (against legalization)
- more people experiment, more people get addicted
- might eventually lead to legalization of all drugs, or a more relaxed attitude towards them
- people might still buy illegal weed of the legal price is too high
- secondhand smoke could reach dangerous levels if people could walk around in public smoking weed