To me the Caad 10 105 is a great bike for the money when you increase the price $600 you get close to other (better?) carbon bikes. At the higher price point I would look at Scott and many others.
The 105 system is good and the only advantage to Ultegria is a small weight difference.
Just get the 105 and you will be very happy and yes you could spend the extra money on wheels which is a bigger improvement.
Last edited by v70cat; 03-24-12 at 04:53 AM.