What are common problems with Audi's quattro all-wheel drive system?

I've heard that Audi's quattro all-wheel drive system is known for its superior performance, but are there any common issues or complaints with it? I want to make sure I'm aware of any potential problems before purchasing an Audi model with this system.

The quattro all-wheel drive system is certainly a standout feature of Audi vehicles, but some common issues have been reported. For example, the transfer case in certain models can fail prematurely, leading to expensive repairs.