BMW xdrive... Any good?

[Mrinsignia]

I will be looking at a BMW 435d at the weekend and it has xdrive? What are people's experience of this? I had a friend who had a BMW with it and he moaned that it drank too much fuel. Does xdrive go wrong much? I like BMW's due to the rear wheel drive but open to the planted feel of 4wd, is it possible to turn it off though?