I think the S7 is a cool looking car and it does have race history. It is as close as you get for a race car titled as a road car. I would not really call it kit car, I would call it race car. It is not a luxury sports car. I've been in it on roads both good and bad. On less than stellar roads, it will absolutely jar your fillings loose. It's hard to get in and out of and is spartan. Because of the asymmetrical cockpit, the passenger has a teeny tiny footwell. It has a colorful reputation for mechanical quality control. I will never forget listening to Lee Saunders, who clearly has balls the size of boulders, keeping his right foot planted for an eternity trying to knick 200 mph on the runway in one at Oscoda during the inaugural Car and Driver 0-200-0 shootout. I think he could spit over the edge at the end of the 13k foot runway when he managed to stop.
If I had a mega dollar collection and was looking to tick off every box, I would probably have one. As garage art or a car to draw a crowd, it has star quality. As a car for pure road driving fun or enjoyment, it would not be near the top of my list.