Thanks for replies so far - actually did not expect so many so I guess this GS helmet has been of interest.
Re sun. I find riding into low sun difficult(problem is worse as you get older). A dark sun visor is of little help since pupils are already constricted by the bright light and then the road surface is so dark it is almost impossible to see where you are going! (my riding is mainly rural roads with ill defined edges). From past experience a peak enables one to dip ones head, effectively shading the eyes. It's a compromise. A sun visor is useful in bright sunlight, though I prefer polarising sunglasses.
Very difficult to find technical info about the GS helmet but I do believe it uses carbon fibre and is lighter than shown in the article.
I have tried one on and found it comfortable(though one I tried was a size too small), ergonomics seemed good, though not keen on double D fastener. A little worried about length of chin piece making lateral obsevations difficult. Trouble is with any helmet purchase you really need to road test it....