Since no one from Colorado seems to have replied, been here since 2010 and I'd say nothing has really changed since legalization. I do believe that there is some method for testing driving under the influence amounts if you get pulled over, but I couldn't tell any specifics (we've had it for a while now, so they must have thought of something).
Though now people often suggest trying to solve any funding problems that come along by using taxes from marijuana, as if it brings in an extra trillion dollars. They did set the taxes here crazy high, like 25-30%.
I don't smoke, but it's nice that my wife can take a hit or two to help her anxiety if we are at a party, or (ironically?) a beerfest since she doesn't drink much.