Hopefully Jones will fill us in when if see's this, but IIRC the maintance is very bad on those.
I assume it's basically the same engine as the V8 S4, just turboed.
This is what he said in another thread about the V8 S4. ~$7k for the timing chain/guides maintenance and it's every 60-70k in the S4. IIRC because of the turboed engine and more power/tq it's every 30 or 35kmi in the RS6.
http://www.columbusracing.com/forums/showpost.php?p=1037687&postcount=33
There's a reason a (clean, low mileage) 6 year old car that was something like $80-100k new is selling for $25k.
If it's got the maintenance records, you don't put many miles on it and are willing to pay the $$$$$ for maintenance, they I'd say why not.
If the timing chain interval is what I'm remembering I'd have to do it every 1.5 years in that car.
But yeah, I still want one.