I live where it's been legalised, and overall I think the effect has been more negative than I had anticipated.
There has certainly been an uptick in use, impaired diving which now surpassed impaired driving with alcohol, hospitalisation due to over-use, and cases of poisonings of children and dogs.
I think what surprised me more is the extent to which many people seem to think that because it has been legalised now it must mean that it's quite safe, without serious side effects or risks. I guess in a way it makes sense though, the government are always trying to discourage people from smoking tobacco, telling about the terrible effects and showing awful pictures of what happens to your body. Not to mention all the other unhealthy things they campaign against. So people, logically enough, conclude that if they are actively promoting cannabis it must be just fine. There has also been a huge jump in dodgy woo health stuff around it, so that probably contributes as well.
Beyond that, as more research is being done, more risks keep turning up, so that's concerning as well, plus the risks for young people and psychosis and schizophrenia. And vaping appears to be as bad as smoking in it's own way.