There are still issues to be worked out on enforcement, penalties, locations, etc. The majority of the retail outlets are in Denver city limits, municipalities can refuse to issue business licenses to retail vendors.
No "public" consumption but if you're sitting on your own front/back porch you're ok, no "pot clubs" are allowed either. The ski resorts are not allowing pot to be smoked on the slopes or in the hotel rooms.
There are requirements on packaging, it's is very heavily taxed and even the lead attorney for most of the dispensaries/outlets foolishly got arrested this past Sept. at a Rockies game when he lit up on a concourse (this was before the new law went into effect but still illegal). He then "lit" up the cops claiming he was a "big trophy" for them, idiot.
Now a new problem for the retailers is how provide their products in child resistant packaging (basically 20 out of 25 5 yr olds can't open the package according to ASTM guidelines).
As for the rally on 4/20, last year there was a shooting at the big gathering in Denver, no fatalities but a few wounded (including a dog), at the Univ. of Colo. in Boulder the campus was effectively shut down for the afternoon, no access unless you had a Uni i.d., the quad was taped off, University cops were everywhere and absolutely nothing happened-yay! My older son has a long time friend that was a sgt. there at the time, he commented on how it was the most quiet he'd ever seen the campus.
Yeah, the brain trust in our legislature sure handled this whole thing well-don't even get me started on the stupid new gun laws that went into effect this past July!!!!