It's certainly looks like being a fantastic car - I've sat in a couple and it has simply the finest interior I've ever seen. The technology is phenomenal and I'm really looking forward to my test drive next weekend. I expect it will sound quite similar to our ML63, which definitely isn't as aggressive sounding as the 6.2 - it's still a very good sound, just turned down to 7.
However, I'm not sure I'd actually buy an S63 - it will be a financial disaster from new. I also wonder if, a bit like my recent BMW M6 was, is it going to be too good to actually enjoy it? If I could get a deal to mitigate some of the depreciation then it would definitely be worth considering but I think that's unlikely for some time. I think my direction will be AMG GT which will be significantly cheaper, more fun and probably more financially stable. I'm in no doubt though, the S63 will likely be the 'better' car.