I think a president - any president - who isn't seeming to take sufficient action gets criticized. I think going and visiting is used as a substitute, a sop, a fake-out, to substitute for real action.
Bush not going to Katrina isn't why he was criticized, the lack of federal government help was. But he's far from the only President to feel, or maybe even be told he needs to visit all these locations or else people will think he's doing nothing - the media loves the photo op, and simple dry facts of emergency plans and actions just aren't sexy enough.
Still, I'd like to see a president have the guts to say that they're adequately briefed, and they're personally making sure the affected area has all necessary federal help - and do so - and leave it at that. Photo ops with some poor family - I'm not real big on those. Definitely not with the President - maybe the mayor, governor, people directly responsible for the area.