In 1997, on my first real climbing trip, me and Victor stopped in Boulder.
Victor is a very good climber, but in Romania protection consists exclusively of fixed pins, so that left it up to me to do the leading. As I've only led (and actually only climbed) very easy routes at the Gunks I voted on a decidedly gradual approach. Our first climb was going to be the classic East Face route on the Third Flatiron, then we would try some harder climbs. We didn't actually climb the classic route.
Climbing the Flatirons was really fun for me. They are giant low-angle slabs, very friction friendly. On the routes that we did, there are plenty of pockets for the hands. If you don't mind being run out a little bit you'll have a blast. Leading pitch after pitch after pitch was a new thing for me, and I found it to my liking. Seems like the classic East Face route would be a great first climb ever (on an uncrowded day). At 5.2 or less, with bolts at the belays and a nice summit, sure beats thrashing up some 5.8 toprope at your local crag, or at the gym. The one caveat in this scenario is that one must be fully competent to manage a retreat with a total newbe. This retreat question seemed to always be pertinent to us on this trip, given the weather, as it would pretty much rain every afternoon, although it was impossible to predict for how long.
All is in the details (pictures included) .
On another trip, we tried to hit Eldo Canyon on the first day, straight after flying in.