First ride out today wearing my C4. Got to say it seems to become more comfortable quite quickly. Helmet itself seems well made, but I too found it difficult at times to tell if the chin vent was open. Good airflow over the top of the head.
Typical Scottish day, so didn't really get to try the sun visor, but I can testify that I didn't get torrents of rainwater running down the inside of the visor. What I did get however, can be seen in this photo.
The misting was below my sight line, but I still wouldn't expect it in a helmet of this price.
Regarding the noise level, bearing in mind I'm comparing it with an old System 5, I found it quite a bit quieter, but I never used to use the removable chin skirt on my old helmet, so that may explain it.
Something to be aware of if you need the XL upwards, is that it is an extremely tight fight into the standard GSA topbox.
Regarding the comms, when working they were very good, crystal clear on GPS instructions, music, phone and also rider-rider intercom. The buttons are small, and quite awkward to reach, so perhaps consider the remote. I would have done, but don't like the thought of paying £100 for the Schuberth version when the SENA 10U includes it in the price. Any problems that I had with making calls etc may be down to my lack of familiarity, so I'll hold back on commenting yet.
Iain