I've been listening to older Rush again lately and I've rediscovered what I loved so much about Neil's playing. First of all, what he played sounded fresh and his technique was really clean. But most of all, it's what Neil talked about in that video clip from the Strombolopolous show; his compositional sense. He starts out by stating a theme and then he messes with it all kinds of different ways as the song progresses.
Here's a fun one from A Farewell To Kings: http://youtu.be/cu1UIEQ5QGs
Neil's part really takes off around the 3:13 mark.