The problem with the A8 in the USA is that it's completely under the radar. Only 2000 a year are sold in all of North America.
The body, interior, and engine are absolutely bullet proof. The transmission is a problem, but there's a handy fellow in Chicago who came up from the Audi online community (think BK, I suppose) and has a nice little transmission shop which specializes in rebuilds on the A8. Excellent prices for members of the community. About 1/6th what Audi charges. Expect trans issues between 100k miles and 200k miles, requiring a rebuild.
I got mine after it's 3yr corporate lease expired from some fat cat CEO in NJ via an Audi specialist broker .. paid 27k. I suppose for that price I could have had a brand new Saturn sedan .. or a world class flagship saloon ... no contest, really.