Uthman burned many Qur'ans (I wonder why this doesn't create many riots). Each of the Qur'ans burned were slightly different than his official version. Uthman, not wanting different opinions, then burn all versions he consider "false".
The thing is, how does he know that the version he burned is the false one and the one he keep is the correct one?
In other cultures, those differences are a clue on what might have been the original. If we have several different versions of Bible (see: hermeneutics.SE), for example, the difference can give some clue on how the Bible might have changed.
Here, it seems that some part of the Bible is modified to support monotheism. I wonder if same thing happen in Qur'an. However, there is no way to know because all other versions are burnt by Uthman. Are there any other ancient version of Qur'an that slightly differ and written before the burning?
Also Answering-Islam seems to suggest that there are many textual variants where no body knows which one is right:
Most Muslims claim that the text of the Qur'an is identical to that received by Muhammad. This is a convenient thing to believe, but is it the truth? There is overwhelming evidence that it is not.