Pros:

• it makes weed cheaper, safer
• you know exactly what you're getting since there's no incentive to illegally lace weed with other dangerous stuff
• less need to prosecute drug possession "crimes" that hurt nobody
• It makes it less appealing to young kids because the dangerous aspect is removed

Cons:

• Weed smells bad to many people, there are complaints from a lot who visit about how open weed smoking make some places smell awful
• Legal Grow op greenhouses cause a lot of light pollution which is an annoyance for the local population
• Some weed smokers joke around saying weed was more fun when it was illegal.
• Harder to enforce impairment since weed takes much longer to stop registering on tests than you are affected by it

I'm not a regular smoker, I think we are better off having it legal though.