I have the Race Star Flex in matte black carbon fiber, and I had it's predecessor.
I think the photochromatic lense is a must have: no monkeying around with visors, sun glasses or shields. It adjusts quickly. On the downside, I think the photochromatic capability wears off and the shield needs to be replaced after a few seasons. Still I think it's worth it. My advice is to rinse it with water only, no soap.
I've been extremely happy with my Bell helmets, and one thing to consider is that of the major manufacturers out there, I think only Bell is doing serious research into improving safety and survivability (at least that's what I read somewhere a couple of years back). Other manufacturers have achieved a reasonable level of safety and compete on features.
The flex incorporates 2 layers of foam to provide protection for both high and low speed impacts. This overcomes the problem that earlier race helmets had where the rider would sometimes be better off with a cheaper helmet in a low speed crash because the hard foam in race helmets was designed to absorb high speed impacts. The other thing that the flex provides is that it will absorb some rotational force as well (hence the name).
But if you're looking for decent graphics, look elsewhere. In my opinion, Bell's offerings are pretty boring.
As far as the Cardo goes, I didn't think it will fit the Bell Race Star.
