I've seen a few people casually write about how they know God's character—the features and traits that make up His person or existence—yet I've always been taught the opposite (that we can't possibly comprehend his true nature), and upon thinking about it myself I don't see how anyone can really claim otherwise. Yes, we have the Bible, but the Bible only suggests how God wants us to see him as; it does not necessarily show how He truly is. God is the totality of everything; His awesome magnificence is beyond everything our puny minds can comprehend. I find it an insult to God to suggest that we can begin to define him. Specifically, to attribute characteristics to God is to say He is one thing but not another, which in effect is trying to make God human. I like to think of God as more complete than the universe itself, not some bearded guy in the clouds; something that cannot be named or defined, shaped or molded by mere words.
I would say this is a common view in my area (Boston, MA, USA). Are we just a minority who thinks this way? Can we really know anything about God's character?
Note: To be clear, you can use Biblical sources but I'm not sure they will be of great use here; even if the Bible was written directly by God, we could never really prove that it was more than what He wanted us to think about him, rather than how He really is. This is more of a philosophical question pertaining to epistemology — the source and scope of knowledge in general. In theory, it could be placed in Philosophy.SE, but being about the Christian God it's certainly relevant here, and also I'm particularly interested in what other Christian's have to say on this topic, and why they might think they can conclude anything certain about the nature of God's character.