I have the exact same wheels on my other bike (Trek 5200/Dura Ace/Mavic K-ES) so it wasn't the wheels. I expected the C'dale to be better as it is lighter and newer technology, but I wasn't expecting such a drastic difference. I can't compare it to the newer bikes on the market but I have been riding for 13yrs so I do have some basis for reference.
I agonized over the decision for a new bike. I looked at Cervelo, Orbea, Isaac, Cannondale, and Trek. Everthing I read about the System Six's predecessor the Six 13 was positive. Based on users reviews of the Six 13 and the improvements C'dale built into the System Six, I decided to give it a try. I'm definately not disapointed. I wouldn't be bold enough to say it is the best bike on the market, but I would certaintly think it can hold it's own against it's competitors.