So a bit of a ride review after 4 or 5 25-35 mi rides. By way of background, I've been riding quality bikes for 35 years, and have had during that time high end steel, titanium and carbon bikes. Current stable, other than some vintage steel stuff, is a Serotta Ottrott and a custom ti bike. My most recent carbon bikes were a Cento Air Willier, Supersix Evo (pre the aero change) and a custom Berk. I'm small, lightish and have am older with an ftp thats low but appropriate to age and weight.
The x68 is smooth, responsive and agile. It tracks well. We've had some big wind here the last month, and I can attest that combined with the wide carbonspeed wheels it is crosswind stable. It does get pushed a bit, but it doesn't snap in and out of yaw like I'm used to with less modern deep carbon wheels. Like an actual sl8, it likes you to get weight a bit forward on twisty high speed descents-its not twitchy but you do feel more secure if you shift weight forward a bit.
Combo of 30-32 (nominally 30, measured 32) Vittorias and the compliance of the bike make it ride very well for a carbon racebike. Does it feel plush? Not if your viewpoint is a ti or steel bike, for an agressive carbon bike its very nice. Over single bumps and cracks its very comfy. I did notice that over "broken" areas of pavement wit high frequency hits the bike does slightly betray its responsiveness and agility with a little rear end chatter, but nothing serious. The front end of the bike is not as plush as the rear, but it does, to me anyway, seem on a par with or even a little plusher than the bikes I've had with Enve carbon forks for example.
With brand new calipers pads and rotors I could generate a tiny bit of brake noise when climbing hard standing, but that seems to be going away a bit as everything settles in.
Leaving aside for a moment how close it is to an sl8, its a helluva deal for what tantan is charging. And if the actual sl8 is all that much better, it must be on another planet.