I've flown DEN-AMA on ZK more than I'd like to admit. Takes too long but good view and I enjoyed the view into the cockpit. You do get RDM but have to check in before the flight. The folks are nice enough. One thing I want to point out is that if your baggage is delayed/lost, there is nothing UA can do in terms of compensation as it's not a UX flight. I had my bags lost courtesy OO in DEN for 2 days on a conx in DEN and I couldn't even get a token $200 for clothes for my presentation the next day.