The problem with McCain is that he wouldn't be that much of a problem if he were a Democrat. As a Republican, he picks just the right moment to hit us in the back of the knees and take away political momentum.
While I voted for him, I suspect he might have done more damage than Zero. One of the nice things about the Bamster is he's lazy. Hillary and her flying monkeys made sure that legislation was prepared and in the works when she was in the WH. Obama tells congress, "Ya'll take care of this." and goes and eats ice cream. One thing I noticed early in this administration is that a lot of the cabinet seats simply weren't filled, the WH had no basic stimulus package legislation prepared beyond, "gimme some money so I can fix stuff" and that important decisions weren't made badly, they just weren't made.
With McCain in the WH, and the makeup of congress being the same, health care passes. It probably would have a few different dog scraps thrown to Republicans, like "The NY Times will say nice things about President McCain for a period of two weeks" but essentially, the driving force behind this was Pelosi, not the Bamster. With McCain in the WH, there's no way the Republican minority could have held firm against a president from their own party, and make no mistake, McCain would have signed off on it after requesting a couple of flourishes for window dressing.