I only observed John McCain make eye contact with Barack Obama once during the debate while Obama was speaking to him: when Obama said, "John," and then pointed out that McCain voted with Bush 90% of the time. And it really wasn't a look. It was more of an obligatory glance at his name being called before grimacing as if he were mad, and then even sneering at times.
Otherwise, McCain seemed to look disdainfully away from Obama while the latter was speaking, as if he didn't even believe he should be sharing the stage with the Democratic presidential nominee.
I thought that, in comparison, Obama consistently appeared a lot less grumpy and aloof when McCain spoke.
UPDATE: More on McCain's utter contempt for Obama: