On this wonderful pi day I think it's worth linking to this:
The Pi Manifesto
No, really, pi is right. Tau is unnecessary.
"The concept of π has been around since the time of the ancient Babylonians (the greek letter representing this number was popularized by Euler in the 18th century)... so why change now and trash it? This isn't the first thing that physicists have tried to change in the field of mathematics (notation wise, anyways)."
http://www.thepimanifesto.com/