They fixed the loosening with a steel fixing bolt that comes stock on all the newer cranks.
I have a pair that are about 3 years old. They've been trouble free after the initial install through grit, grime, rain, and snow. My only real gripe is that I needed a special spanner to tighten the lockring around the self-extracting fixing bolt. They also use a different BB from the rest of the FSA line.
If you were going to get a CinQo, I would say its a good crank to go with. Otherwise, you might look at the Ultegra or Rival cranksets instead. You're not really gaining any stiffness with the FSA carbon arms, and the weight difference is negligible.