I've been riding the C7's for sometime now and they're OK. They have noticeable flex, even at my 130lbs. They were a bit scarey on some descents earlier this year equipped with ultegra pads. I recently put the planet x's on my race bike, although they seem to have less flex, I haven't had them out on the road, as I'm recovering from a broken collar bone. The dual pivot design is better, but I feel like KCNC just took too much material off the C7's. I'll report back in 2 weeks when I'm back on the bike.
Thanks for your info, and I hope your collarbone gets better soon. If that's what these kcnc brakes can do then best I avoid them! I'll play it safe and get the planet x ones. The colour I like is out of stock, which gives me more time to read more reviews, but when I finally buy some brakes, a detailed review will be on it's way.