I think most people immediately assume the R-Class is a bad car because of the contraversial styling.
I remember I thought along those lines. The question kept arising in me as to why Mercedes would build this thing? Then, I was able to sample the R-Class for a testdrive and I came away impressed, but not won over.
One thing is clear. If you have a big family and like to travel, this really is a very appealing car. It's got safety, interior space, 4Matic and it is comfortable too. Sure, the styling doesn't appeal to everyone, but I know a guy who bought an R280 CDI 4Matic because of the qualities of the car - not the style. He said the car was perfect for him and his family and he regularly uses it to drive down to Italy or Southern France.
Personally, I'd rather have a GL320 CDI or an ML320 CDI or even an E320 CDI T-Modell, but I do see the appeal of the R-Class.