I had a C2 and found the visor would not stay up above 30mph, no matter how many times I adjusted the tightness of the retaining mechanism, and the removable lining was held on by cheap velcro fasteners that were always lifting away from the lining. It had the poppers in situ for securing the lining (as in the System 4) but Schuberth had chosen not to use them. It was also noisier than my old System 4 when used on the GS.
I had to replace it due to knocking it off the bike seat and chose a System 5. For me it's a much better helmet. The visor stays up, the removable lining is secured in a better way and it is quieter.