Representing the USA abroad and being the "focal point" in foreign relations - that is the most important role that the US presidents plays - in terms of actual implications. Domestically it does not matter as much, but internationally it has a lot more impact - as the leaders who meet get "much more work done" in between them. Therefore a smart and effective diplomat is most beneficial to the position as president. Too bad the US population is so little aware of this...
Of course it matters. President Gore would not have ignored the Hart-Rudman Report the way Bush-Cheney did and 9/11 would not have happened. Think about it: no 9/11 in America. Hell yes, it matters who is in charge. DUH!! Obama has some serious work cut out for himself and Biden but at least with them there's a chance that work will be done. With McSame-Palin, it's business as usual: continuing the last 8 years for the next 4.