I read an article about this recently, it's definitely interesting.  The one place where I haven't seen it mentioned is what happens when you want the area of a circle, since that necessarily involves the radius.  I'd guess you'd have to use τ/2 * r^2, but even then, that's one formula vs. the rest.  It's probably a good tradeoff.  I can definitely see the advantage when using radians.  Never thought I'd have to re-learn trig again...