It definitely depends on the narrator. Stephen Fry reading anything is wonderful, and I loved listening to audio versions of Jane Austen books by English actresses like Anna Massey and Joanna David. Simon Callow reading P.G. Wodehouse is also a perfect match.
On the other hand, I've been trying to find some of my favourite books on audio books, but I find some of the readers irritating, and don't work at all. Fortunately, being able to listen to a short sample on iTunes means I haven't wasted any money on a book I wouldn't be able to listen to.