I drove a "regular" SLS on the track in Florida last December. Although it was "objectively" amazing, I didn't like it. It had incredible grip and power and sounded amazing. However, I found the seating position to be too low and the car felt simply HUGE. It isn't but the front is so long it feels like it. It felt so big (not heavy but large) that it didn't feel sporty to me if that makes any sense. The SLS BS will be an absolute beast and put down incredible numbers I'm sure but, for the money, I would personally go a different route. I would take a C63 BS over the SLS BS any day even though it a clear step down in ultimate performance. Just my opinion which I'm sure many would disagree with but there was something "subjective" about the SLS that I just didn't like.
BMW really needs to build a supercar to compete with the GT2/GT3 RS, the SLS BS, etc.