Because many non-Americans favour Obama there is a tendency to see McCain as the opposite of what they favour and all bad. I am not sure this is true - he is not GWB. He clearly has a lot more intelligence and he can make fun of himself rather than have everyone else do it for him!!
My biggest concern with McCain is that he is a lot more hawkish than Obama but I do think that he would be a lot more practical and considered about the way he acted.
It is not the way I would like it to go but it would NOT be a disaster. Other governments would work with him (just as they have with the far worse option of GWB).
It would be a 5 minute wonder but then the world would settle back into getting on with it.

I will speak strictly from the American perspective...McCain plans to tax health care for the first time in our history. Many people are extremely upset about this as our health care is expensive enough as it is. Personally, I pay over $400.00 a month for my family and I to have medical, dental, and a $500,000 life insurance policy on myself if something were to happen to me. Too expensive as it is, and now you want to tax it? That is one of the biggest strikes against McCain as far as his policies go. The biggest backlash if McCain wins, will be from the black and minority community. There will most certainly be cries of racism from a lot of people as the early polls show that Obama has almost a 10 percent lead on McCain. If McCain were to end up winning, I suspect there will be rioting, picketing, and protesting from a lot of the black and minority communities over a perceived injustice. This will be a really bad way to start his Presidency and I can only see it going down from there. If people are outraged before he even takes the oath of office, his Presidency is doomed to fail, no matter what policies he enacts or changes he makes. He will always be known as the white racist who held the more deserving black man down. Just my opinion only obviously.