I think we are able to understand the concepts of omni-traits, to coin a term. But we need to define what this means for any specific individual. The Bible only vaguely describes Yahweh's traits; the descriptions of god as all-knowing or all-powerful are later interpretations and come across as conveniences. And attributing such traits to Yahweh creates problems that I think cannot be resolved, which is when we turn to the incomprehensibility of god as a way to deal with them.
However... until we get to one of those difficult issues, we seem to have no problem at all comprehending god. We have a clear basis for judging his character and actions as long as they fit into an acceptable moral framework. When his actions fall into a gray area, we decide that he is inscrutable. That we cannot fathom his ways. That he exists on a higher moral and ethical plane, and thus our judgments do not apply.
If god is inscrutable, then we do him a disservice by trying to explain his actions. This leaves us in the uncomfortable position of realizing that god can do or be anything, because our notions of good/right/moral/etc do not apply to him. When combined with the actions he takes (according to the Bible), the picture we get is a concerning one. His quick temper and willingness to solve problems by killing should make the believer very nervous.