I bought a lightly-used S1 Schuberth off of eBay this summer. Overall, I am very pleased with the Schuberth. It is a typical German product, high quality and lots of thought was put into the design. The functional items like the venting system, the tinted visor, the face shield changes, and the strap release are fantastic.
The S1 is way quieter than my Shoei RF800 was. Like was metioned before, you can immediately tell when trying it on in the dealership...you can't hear anything. When you crack open the visor while moving, the noise is virtually identical to any other helmet.
The flip-down tinted visor is great. I don't ride with separate sunglasses anymore. The outside tab to activate the visor is easy-to-use and works well. People do give you looks because you look like a fighter pilot.
The inaugural ride with the Schuberth was a 1,000-mile weekend ride to Vermont in 95-degree F (35-degree C) heat and intense humidity. The weather was brutal. I was initially a little disappointed in the venting until I came to my senses and realized that nothing would overcome those conditions! Since the baking ride to Vermont, I have ridden in slightly cooler conditions. Those conditions made me realize that the venting is probably the best available in a helmet today.
I see very few of these helmets and enjoy the exclusivity of having something unusual. If you put the Arai or Shoei name on this helmet, people would never stop raving about them.
Now that I think about it, I wouldn't go back to anything else but a Schuberth.