I have a carbon Cervelo and a steel Bianchi (and used to have the aluminum CAAD9). I bought the steel frame to convert it to a travel bike with S&S couplers.

The steel frame wasn't very expensive but I could easily live with it as my only bike. It isn't as stiff or as fast as the Cervelo but it is very comfortable and just rides nice (hard to even put into words). The CAAD9 was a good bike but clearly my least favorite. It was kind of a rattletrap on rougher roads and on long rides.