Had to comment, even though this thread has been around for ages. I enjoy listening to Peart even now, although it's different that when I listened 25 years ago.
One of the things that people touch on over and over again is his consistency of delivery. But while I am sure he vamped a lot when they were writing and testing out new songs, there is something else at play here. One of the things I really respect about Neil is his composition of the drum track. By his own admission, he scores his own work like a dancer or ice skater would learn a new routine. It's all about telling the story, no different than how the vocalist or guitarist tells it. I learned from him that scoring a part can help transport the listener or it can hinder them. There are rules within music theory as well as popular music. They are important because they are the history of vocabulary by which you start telling your story. Do you push the song or do you pull it? Straight time, double time or half time? All of these choices play into the mood you create for the listener. He builds his groove, building his fills as well and sometimes breaking down the groove altogether the second time through. Others known for progressive styles have tried this. Some succeeded and some failed in their telling of the story. It is that grasp of the theory and history of drumming that excites me when I hear Neil.
The other thing that impressed me is that he has continued to seek out others who would help him hone his craft. Even after all these years, he continues to look up other drummers who might help him learn a thing or two.