While the R8 is a great car (especially the V10 Spyder ) and a good all round every day car, it is a bit more of a, em, 'Prima Donna' than the LS 400! One thing to watch out for are that there are only certain Audi dealers who have R8 trained 'technicians' (ah, remember when we had mechanics?!). Still, in Scotland, there are more of them than the two Lexus dealers we currently have!
It is so annoying when things are not right with cars! My wife just sighs and lets me rant and rave - well, to a point! She told me today that I had "extreme OCD with your (flippin') cars" as I was trying to trace a tiny rattle in the Daimler's driver's door! Found it though! Ha!
I hope your LS gets fixed to your satisfaction.