The first thing comes to mind about what I learned from him was, regardless you are student or professional, if you don't play great, you are nothing.
George loved who plays with passion. When he likes someone blowing his/her solo with high energy, George walks up and starts screaming "Go! Go! Go!".
George didn't approve lyrical improvisation. He called it "White Bread". I witnessed quite a few students who plays with nice groove but rather lyrical than energy crashed by George, which taught me that one must be able to play with the style that is asked for the music. There is no point to be defensive about your style when band leader asked otherwise.
Me? I was lucky. I loved George's music. I had the same passion to blow as George wanted. George never liked flute. Heck he even doesn't like soprano sax. His hearing was bothered by higher frequency. Despite that, he kept me around. I was really, really lucky.