He has a very developed style. You can see the obvious resemblences of his style and Stevie Ray Vaughans style... But truth be told when John was younger he wanted to be a metal virtuoso. Instead the blues got ahold of him and now he has the style that we've come to know. Like Schmange said... its a comfort thing. He gets in a groove and just plays. Its something that you have to mess around with to be able to know what sounds good and what doesn't.