I just started biking this summer. My fiance bought himslef a Cannondale R7000 this spring, so I started riding with him on my cheapie Target mountain bike until I decided I liked it enought to get a real road bike of my own. So, about a month ago, I got a Trek Pilot 2.1. I love the bike, and I especially LOVE how much better and farther I can ride on it. So, that leads me to my question...what do you consider a challenging ride? How far do you go? How much of your ride is flat or has hills? I have been riding 20 miles pretty consistently at about 17 mph with mostly flat and some hills.