It depends on the issue.
I see capitalism as something that needs to be done away with, so I guess I qualify as an extremist on that matter.
On most contemporary political debates in the US, I am definately in the middle, to a great extent because I think the parties stopped actually discussing the issues a long time ago. For example, I think abortion should be legal, but heavily regulated, and difficult to get.
On most matters I find my opinions sometimes change, whether from new arguments or new evidence, and that willingness to consider new information is probably what makes a 'moderate' or 'centrist'.