Nesh and I spent the weekend getting through the audiobook version of "Ender's Shadow" and we were completely enthralled by the content. We've both read the book( multiple times ) and are very familiar with the storylines. The audiobook was quite unique. Each chapter with a unique voice( Poke, Sister Carlotta, Bean, Col. Graff, etc ) is given a different reader. Some of the chapters are even given multiple voices. It was uniquely done.
I loved this series, but haven't heard any of them on audio book.
If you are looking for a really good sci-fi audio book, I suggest Diamond Age.