The Lebanon Daily Star has an interesting article about a current project to produce a critical edition of the Qur'an influenced by manuscripts found in Sana'a which differ from the standard text. Muslims, of course, consider the Qur'an the divinely revealed word of God, and hence do not subject it to the same styles of exegesis you find among many Christians with the Bible, though the interpretation of the Qur'an by Muslim scholars is more complicated than generally believed by the average non-Muslim. However, the standard edition of the Qur'an was actually compiled during the reign of the caliph Uthman, and hence there is a certain room for uncertainty as to what other versions of the text might have existed.

Another issue discussed in the article is the possibility that many of the words in the text are not Arabic, but loanwords from Aramaic or Syraic used to express concepts not found in 7th-century Arabic. Looking at these two languages for clues has led scholars to some interesting conclusions, such as the theory that the righteous will receive in heaven not beautiful virgins, but grapes. (Incidentally, such a conclusion would remove the main incentive for me to ever convert to Islam.) I am in no way qualified to discuss this article much further...if you're interested, read the whole thing.