I love audio books, I listen to approx 6hrs of audiobooks/day while I'm working. But yes, as someone mentioned earlier, narrators are either great or terrible. I find the narrators who put too much effort into using different voices are the worst though.
I don't know what you're into, but I find that heavy books like philosophy are terrible in audio form, but all of the best fiction ever written is great in audio. A lot of historical audiobooks are great too.