Doug has some interesting things to say about John's gospel here, principally he argues that "Jesus didn’t run round saying all those “I am …” claims that he makes in John’s gospel. The speech of Jesus in the gospel is largely a stylised representation of Jesus’ significance, given narrative form within the newly established genre of gospel."
I agree with this. That is, I don't read John's gospel as primarily an historical document (I think the synoptics are primarily historical, with the theology more or less thrown in). What I do think John's gospel is, however, is divinely inspired. I think that it tells the truth about Jesus, and it uses the monologues to portray that truth dramatically. I realised the other day, when pondering the question of inerrancy, that as soon as you let go of the modernist mind-set, and allow inerrancy to mean something other than the Enlightenment-era construct of historically demonstrable fact, then I would want to argue quite strongly for the inerrancy of John's gospel (and, flowing from that, the inerrancy of Scripture as a whole).
Which is a deeply conservative conclusion from what might seem a liberal premise. Yet it's only a liberal premise if you are, yourself, completely conditioned by Modern liberal prejudice.
Such is the world we live in.