FYI, the latest issue of ProCycling magazine (#128, August 2009) has a great article with a technical and ride comparison between a 1983 (on the edge of on-topic ...) Pinarello with a Campagnolo Super Record group and a 2009 Lapierre with a full pro team rig.
They had a reasonable methodology to try to compare just the bikes, and tested each with several riders. Short version is about 10 watts more developed on the new bike (stiffer) translating to about 3 to 5 kph speed gain.
Good reading - and it seems the experience on the older bike made the young French riders greatly increase their respect for racers of yester-year.
Stratham, New Hampshire, US