I rotated there. You do 2 weeks at Denver General which is pretty much straight trauma with occasional joints, hand, and sports stuff being done in the ORs. The other 2 weeks you have the choice of the VA, Univ of CO Hospital, or the peds hospital. It seems like the VA is the best experience for most of the rotators as you get to do more and the attending who works over there is a little more vocal in the selection process. I personally was over at the university hospital which I was not a huge fan of as it is basically 6 joints cases every day where you get to do absolutely nothing.
One thing I would suggest is rotate there early in the season. It seems that the people who did had a LOT better experience overall, got to do more in the OR, enjoyed themselves, etc.
Overall, I think you would get good training there, Denver is awesome, you can ski a lot. I ended up matching somewhere higher on my list (I didn't end up ranking Colorado very high). If you have any questions, ask away.