I've ridden with C-Cadence several times & have liked it quite a bit.
However, today I got distracted just as the pack was going downhill and fell off the back before I looked up.
I'm not great at downhill to begin with, and my trainer difficulty is set at 50%.
I was on the Specialized Atheos with the Meilenstein wheels and despite riding at >4.1 w/Kg I couldn't catch up.
But when I've paid attention it hasn't been difficult to stay in the pack.