I went from a bone-jarring, tooth-rattling, 25-year-old Schwinn steel frame to a Habanero titanium (with skinnier, higher-pressure tires), and the difference was night and day. BUT, I can mash those pedals from a dead stop, and the frame doesn't flex--it puts the power to the road.
Of course, I would expect a better ride, as (adjusting for inflation) I paid about 5 times as much for the Ti as I did for the steel (I moved the handlebars, seat and pedals over, so those didn't change anything).