I was about to ask the same question as the original poster. I'm about to replace my 20 year old Cannondale SR800, which is about the stiffest and quickest turning bike ever built. I can't understand the current trend of frame building with a sloping top tube, and shortened seat tube. At first I thought it was because of the weight, but with a now longer top tube with a shorter seat tube it would appear to be a wash. Maybe a bit heavier since you now have to have a longer seat stem. I guess it's all in what people are looking for in comfort, or even looks, but think my next frame will be a conventional racing type diamond.
As an afterthought, how many of the relaxed frames are being ridden in the TdF right now?