It would be easy to see the disapproval of Bush as being some left wing thing--sure they can't stand him, that makes sense. But at 24% approval, it means that about half of the right wing/conservative people who supported Bush, now disapprove of him. That's rather startling.
As for the history thing, I can see what some are saying. Many presidents who were deemed failures in their times are seen as not so bad or pretty good after many many years. I don't see that happening for Bush though, in fact, I think things will get much worse for him if the investigations continue into this misuse of power and the other shady stuff Cheney got up to. However, I do think that history may end up finding that Bush wasn't as malicious as he's currently thought of, just remarkably incompetent.
9/11 (probably) and Katrina (definitely) would have happened to Gore as well. The Iraq war, the torture stuff, Guantanomo Bay, the Plame mess, suspension of habeas corpus, the ire of the international community and everything connected to that is all uniquely Bush. It will have to take Obama or beyond to turn Bush's lemons into lemonade, if such a thing is even possible.
The odd part is, had Bush stayed focused on Afghanistan and not invaded Iraq, he most likely would be viewed quite differently now and I can't even imagine that Obama would have won. Bush's legacy now is tied directly to Obama's. If Obama succeeds as President, then it will be partially because Bush created an environment where Obama could be elected and Bush created enough fires for Obama to put out. If Obama fails, most likely it will be cause Bush's actions were so damaging that they have made it impossible for virtually anyone to do well. So Bush needs Obama to succeed, so history can say that what Bush did was bad and stupid but not irreversible and put the country in a better place from future generations learning what not to do.
I would imagine then, if there are 24% of people who actually support Bush, they should be rooting for Obama to succeed more than anyone else. Logic though has never been their strong suit.