Be sure to check out the rebuttal.

http://tauday.com/tau-manifesto#sec:the_pi_manifesto_a_rebut...

That's hardly a meaningful rebuttal.

  C = 2 * Pi * r = Tau * r
  A = Pi * r ^2 = Tau / 2 * r

PS: When dealing with radians Tau is fine, but I like showing +Pi and -Pi both point away from 0.

> I like showing +Pi and -Pi both point away from 0.

What would be cool is to see two different points showing what the direction is.

c = Pi/2

+c would point upwards, -c would point downwards. 4c is a pizza.

The awesome thing is, today he posted his own rebuttal:

http://spikedmath.com/fact-005.html