What happens is that i feel a confidence with these wheels which is clearly higher than with CCU.
CCU feels quick and nimble. But they also are harder to ride even with wider tires.
It would be really interesting to test 2015 CCU and the forthcoming wider CCU with same tires on same bike.
That would sort out what the wider rim is doing.
Resurrecting an old thread as I've been contemplating Corima wheels but saw this question posed and figured I'd contribute my experience.
I agree that the CCU feel very nimble and quick handling. I partly thought that was due to going back and forth between Boras with 27mm tires and CCUs with 23 but now that I have Boras again with 27mm tires and Lightweight with 22mm, I don't notice the super sharp handling like I did with the CCUs. I almost felt like the CCUs would kill me if I got complacent in a descent and didn't pay attention but when you were paying attention, they cornered very sharply. With my brief time on the new Cosmic Ultimate, they had to be hands down the most stable descending wheel I've ever ridden. Going down a fast descent, it felt like they were self stabilizing, really confidence inspiring.
There's a but in there, both sets of Mavics felt dog turd slow. I've had quite a few other wheels over the past year that have been the same but the "fast" feeling wheels, I can't quite pinpoint what it is about them.
In general, as I move up to larger Veloflex tires, the fast sensation is more pronounced. Enve 3.4 to DT 240S, Enve 3.4 to Wheels Mfg, Enve 4.5 to Tune mig/Mag, Boras and Lightweight all have the special speed sensation. Again, as I move from 27mm Vlaanderen down to 25mm Roubaix to 23 Carbon, the sensation is diminished. The Lightweights with 22mm Extreme still maintain most of the sensation, which is pretty remarkable as I'd say they have a better speed feel than Boras with 25mm tires.
I tried old ccu with 27mm tires and they still felt slow and the new CU with 25mm rubber felt slow too. So, I don't know what it is that make some wheels special.