Got my first carbon when I was around 275, no issues, was a roubaix. Popped 1 spoke on the stock fulcrum wheels, switched to shimano wheels, never had a problem after that.
On a giant defy now still no issues, runs quiet. No weight limit and lifetime warranty. Cannondale lists their weight limits at 300, but most weight limits have to do with the wheels.
I find most of the carbon horror stories are from alarmists...