I can only comment based on my own experience, so here goes.
I always wanted one, loved the look of them and the V10 and Lamborghini connection made it even more desirable in my eyes. I had a PF 4.2 QS for over 9 years and when the chance to buy an S8 came along I took it, it was a
considerable step up. Two years into ownership and I'm still glad I did. It's had it's problems, and has a considerable thirst, but for smiles per mile it's the best car I've ever had, and probably ever will have. I may moan about filling it up with Shell's finest far too often but when the needle is rocketing to 100mph in third gear it makes it all seem worthwhile.
There is plenty of discussion on here about their weaknesses (manifold flaps, power steering hoses) but every car has it's weaknesses, the S8 ones are just inevitably expensive. Borys is selling his, maybe talk to him? Be warned though, once you've driven one you'll want to buy one, so be prepared
