Mostly the people, but I find I get an odd ego-boost from winning a good fight. I don't care about score, a BnZ sortie with 100 kills wouldn't have me even half proud. But when I get in some wicked one on one, pushing my plane to the limits, trying everything I can to the point where my heart is racing and my hands are so sweaty I can barely hold the stick... winning THOSE makes me feel proud.