Well Denver is probably going to see the US version of that, it will be drunken frat boys from Midwest schools instead of football fans and those guys have ruined whole musical scenes. Also if Denver turns into a cesspool of homeless hard drug addicts like Amsterdam or Vancouver it will probably be a short lived experiment and few other places will want to follow. It is important it is done right. The other side would love to see it fail.
We have that now. Its been that way for years. I got pulled over just for turning onto a street in Denver because that street was known for drugs at that time of the morning. I was just trying to get to the McDonald's and I got the fifth degree from the officer that pulled me over. I was in a panic and he didn't believe that I was sober, he made me do a breathalyzer even though I had just come from doing one for probation, insisting that I was acting like I was drunk, then I had to sit there for a half hour while he waited for them to verify that I didn't have a curfew as part of my probation and no warrants in either county I was on probation with...
Needless to say, I never made the mistake of trying to get to that McDonald's from the other direction of Colfax again. In fact, I never went back. :/
We have a sizeable homeless population. There are waiting lists for beds at the homeless shelters and so most go and get drunk so the cops take them to a detox center like Arapahoe House for the night.
Colorado is a beautiful state but Colorado has a lot of problems. They aren't as apparent as places like Texas, California, or New York, but that's just because we don't have the population density of those places. Violent crime in Denver, for example, is 2.5x the level of violent crime in New York City per capita.
All of that aside, legalizing marijuana is really just a matter of making money off of pot sales. Colorado was one of the first states to decriminalize marijuana all the way back in 1975. It was a petty offense with a fine of $100 for possession of an ounce or less. The penalties kick in if you are caught with it in public or caught buying it. Then came MMJ in 2001. Then the city of Denver legalized possession of an ounce or less in 2005 and now we have the state legalization.
What people don't realize is that outright legalization was just a way for the state and local governments to make money off an already existing marijuana trade. The taxes between the state and city are going to add up to 35% of the sales in some areas and outside of that, they are making it ridiculously difficult to get a license to sell it. As a matter of fact, as the law currently stands, only previously-approved medical marijuana facilities are eligible to apply for a retail license and open on January 1st.
If they don't manage this right, they're going to price it out of the market in those areas and increase black market dealing.
Here are the latest statistics between Denver and NY - it looks like either we've gotten better or NY has gotten worse since the old 2006 data.
Denver:
http://www.neighborhoodscout.com/co/denver/crime/
New York City:
http://www.neighborhoodscout.com/ny/new-york/crime/