First was when the slightly raised piece of carbon around the rear brake mounting broke away from the stays, most likely caused by me unknowingly using a bolt 1 or 2 mm too long for the job, and second was the development of a small, purely cosmetic, hairline crack in the paint where the rear stays are shot into the BB. However, both times the frame was replaced in double quick time without question and I've had no problems since.
Weight wise, well, I've lost close to a pound by replacing the 9spd Tiagra with 10spd Ultegra bringing it down to just under 17.5lb. I could probably lose almost another pound off that with a better wheelset.