I don't expect anything to show that Bush had prior knowledge.
However, the memo speaks very directly to all of the "No one could have predicted..." statements that were tossed about. If the hearings accomplish nothing else, then at least we won't hear any more bullshit like that from the administration.
And if I got intellegence that stated: Nevertheless, FBI information since that time indicates patterns of suspicious activity in this country consistent with preparations for hijackings or other types of attacks, including recent surveillance of federal buildings in New York.
...it would scare the bejesus out of me, and I would get directly, personally involved. Maybe it was too much like swatting flies?