I had a C3 with the bluetooth and after two years retired it for a BMW Evo 6 with Bluetooth.
C3 leaked around the visor, dripped on to my nose a few times, and the Bluetooth was just plain rubbish. Customer service was akin to a major UK utility and in the end decided that along with loads of other people the Bluetooth collar was not fit for purpose. Fit was good and could not fault that
Had the Evo for a year now, no leaks and the Bluetooth is much better at connecting to the BMW bike, and the rotary wheel works volume. Had a warranty claim on one speaker, and this was swapped over a weekend and returned fully charged and ready for use. Fit is s bit more snug in the cheeks (face not bottom) but have done a few ten or twelve hour rides without any problems.
I'm sure the interoperability is part of the BMW process to completely assimilate me into BMW branded underwear and the like, but I just can't seem to fault it.