Take a look at the latest issue of Velo. They did another test of aero bikes and the winner is the Cervelo S3. It's not quite as fast as the S5 tested earlier but they said the S3 is more comfortable and cheaper. In fact they claim it's the best suited out of the bikes tested for hours in the saddle with fast rides, including lots of hills. That said that seems to take away the disadvantages of aero bikes, except weight. The Ultegra equipped S3 is 16.5 lbs.