Jason at Occupied with the Word has written a series of posts about audio Bibles. He concludes (with some caveats) that listening to an audio Bible provides a helpful supplement to studying the written text.
His main concern is whether listening to an audio Bible instead of reading the Bible results in our paying more attention to the person reading the Bible than to the text itself (or, ultimately, God). He also has concerns about using an audio Bible as a way to cram Bible study into your schedule rather than scheduling your time around studying the Word.
Jason gives three reasons for listening to the Bible:
Spiritual Growth… As I stated yesterday, audio Bibles used in conjunction with normal reading can accentuate understanding of the text and can also aid in retention. In that way it can be an excellent tool for hiding God’s Word within us. At the same time, some people are auditory learners. That is, they learn better through what they hear than through what they see or read…. History… [Before William Tyndale] much of the learning of the sacred Scriptures was through speech. Obviously this was not recorded speech, but it was through the medium of the spoken word. Through most of biblical history a great majority of people only knew of the Scriptures in this manner. Denying the continuance of this way of learning would be depreciating history. Biblically… In essence God has designed the transmission of His Word from heaven to our hearts through the written word as well as the spoken word. God clearly indicates that learning the Scriptures may take place through the medium of speech. In fact, it is commanded in this text [Deuteronomy 6]!