Here is an excellent contribution on the historicity of the "I Am" sayings by Rob Bowman. I would especially draw attention to reasons 2, 3, 4, 5, 6, and 9 in rebuttal to doubts about the historicity of these parts of John. Some of these I had not thought of explicitly before, particularly reasons 3 and 4.
I have only two caveats, which should not be allowed to obscure the many interesting arguments. I myself would not make a hat-tip to Richard Burridge, or to the supposed discovery that the gospels "are Greco-Roman bioi." I have serious doubts about the strength of the arguments for that thesis.
Second, while I very much appreciate Rob's attempt to distinguish a legitimate from a "too loose" sense of the phrase "ipsissima vox" in New Testament studies, I'm inclined to think that the phrase is an unnecessary technical term and is now causing more confusion than enlightenment. Indeed, in the hands of Craig Evans it is being used as a vehicle for a false dichotomy--either you don't allow for the possibility that, say, Jesus' words were originally uttered in Aramaic and hence not in Greek as in the Gospels, that they had to be translated, or you think that some saying attributed to Jesus might well have never been uttered by him in anything like the form we find it, that the form we find it is a mere elaborative exposition upon some completely different incident as found in the synoptics. If the former is "ipsissima verba" and the latter is taken to be "ipsissima vox," then this is obviously using "ipsissima vox" in what Rob rightly calls a "too loose" sense. But that sense appears to be increasingly common even in evangelical New Testament studies, which means that the phrase carries a false air of technical precision while actually being radically ambiguous. So we might as well do without it. But that's just my opinion on a terminological issue.
Lots of good arguments here, so enjoy the piece.