Strengths: Very efficient power transfer, very confident ride, nice characteristic with eager accelerations.
Beautiful workmanship and tubeshapes, great customer service.
Weaknesses: A teeny bit heavier than the alu/carbon version. Concavity of downtube means noisy ride on gravel.
This is my second Cyfac road bike, the first one being the Nerv alu/carbon (let's called this "old" bike). What a nice surprise going from the alu/carbon mix to the (almost all) carbon!
The older frame was comfortable for long hauls, with some reactivity to the ride, and I thought that it was plenty stiff. Yet this new frame was much stiffer, giving a very efficient power transfer. It is a teeny bit heavier, and more sure-footed than the old bike.
Basically Cyfac gives away some "spring" the ride response and gains a lot of efficiency and stiffness. It still has that refined, confident response of Cyfac frames, but in a more aggressive packaging.