I had the same disappointing experience when I bought my first and only carbon fiber bike which was also a Giant Defy. I was so excited when I bought it. I thought it was going to make a big difference. The only difference I noticed was the added vibration. My hands were always numb. I wanted to like the bike so bad but ended up selling it after about a year. Now I've gone back to steel bikes and would never switch. If your new carbon Defy weighs 20 pounds then both my Serotta and my Gazelle are within a pound and have much better ride quality.