I too own an R3 and while I'm not a Clydesdale, I weigh 165 lbs. The bike IS amazingly super stiff. It's stiffness was compared to many of the name brands. The following link contains the data:
http://www.cervelo.com/reviews/Flexi...%20Muscles.pdf
By design it's vertically compliant so if you ride on rough roads or chip rock, it really smooths the ride significantly. This is in contrast to other stiff bikes that may give a harsher ride. It was actually designed for use by Team CSC on Paris Roubaix for that very reason.
There are a lot of very good bikes out there for sale, but this is one excellent bike IMHO, YMMV.