For years I hesitated to try the audio books because I wasn't sure how the word play would be handled. When I joined audible.com I decided to try and now have them all. I agree with everyone else....Briggs is the best, followed by Planer. Wyrd Sisters is my least favorite witches book but that's probably because of Celia's narration.
I find it impossible to drive, clean my house, do yardwork, or groom dogs without listening to a Discworld novel. In fact I'm about to turn off the computer and wash dogs #3 & 4, with 45 min. left on Men at Arms. I might do Feet of Clay next, but I've had Stephen King's new book for over a month and I need to get a start on it. At 30 hours and 45 min. it's going to take me a while.
My daughter recently asked (as a Discworld book was playing in the background in the car), why I kept listening to the same book over and over again. I then realized that she was just picking up on the narrator's voice and had to explain that they were, in fact, different books, narrated by the same person.