I have a Cervelo RS and love it. Also considered the Giant Defy, Felt Z-series (specifically: Z25 & Z35) and Specialized Roubaix before buying. Look 566 wasn't, unfortunately, available at the time I bought. They're all nice bikes, but I particularly liked the RS and Roubaix. After riding the RS regularly for a couple of years, I'm sure I could handle the more aggressive geometry of an R3 or Tarmac, but I still appreciate the slightly more stable handling of the RS...