I heard about this car ever since it was announced. Yes, there are people out there who don't know what these cars are. But thats their problem. These cars are quite rare also. Unlike Lamborghini's, Ferrari's, Bently's, Rolls Royce's, Maseratti's, Lotus's, and Aston Martin's which I have seen in the streets, I've only seen the Salen S7 in autoshows.
The Salen blows the other's out of the water in performance and speed, and the price isn't actually that bad. I'm more into muscle cars than exotic cars like this, but it's a nice one. Like the owner says, you'll be going so fast and hitting a corner and your mind just says "this isn't possible", but it takes it so fast. It's a really good design.
As for how rare, they are hand made, of course and take a while, but aren't that rare. I'm in a few car clubs and know people with some rare one's, such as a Salen. Personally, I'd prefer a '69 ZL1, but that's me (they are also more money, though). Ultimately, I'd like the one-of-a-kind '68 Z28 Camaro convertible (but it went up to $1.2 mill and the seller didn't accept the bid, last I heard).