Last year, I tested a Domane 4.5, as I was looking to replace my Giant OCR2. I was impressed that the Trek was the smoothest bike I'd ever ridden. Unfortunately, crashed my bike a week later and didn't get to continue testing machines for months.
Trek Demo days are running around here now. Two weeks ago, unable to get on the 4, I plopped onto a 6 series, provided by the LBS at a tent on one of our local roads. It only had 23's and was poorly fitted for me. I was surprised at just how harsh it was.
Today, saw another demo tent and they only had a 5.9. Funny...smoother than the 6, but slightly large for me as I was on a 56, but probably need 54. Very nice ride on good pavement and not bad at all on the rougher surfaces. I liked it better than the 6.
Now I gotta go back and try the 4.3, which is in my price range. Should be interesting...maybe it's smoother because it's heavier!
Others on my list include the Scott CR1, a favorite at the LBS I ride with. Tried the Giant Defy Advanced already.
Yeah, I know I should try the Spec. also.