Headers, worth it?

Seems to be a lot of talk about this lately... Some for, some against...
First of all please do not post drivel in this thread. We want this thread to be an informative and actually useful. Preferentially with some real facts/data

From my internet research it seems the boys in the US of A are getting some good gains on the factory STI turbo by upgrading the factory header.
We know what their dynos are like. So I am sure we would all like to see, what gains if any are available in Australian dyno terms.

What I am looking for is comparisons showing before and after dyno results or secondly people with 1st hand experience. I am personally am most interested mostly in mid-range torque gains (area under the curve) and spool changes from equal length headers.

From reading discussions in other threads the conclusion seems to be that there is not much (if any) to be gained from upgrading the factory Subaru twinscroll header (at least on the standard turbo). This discussion is not about that, this is for non-special Subarus with the standard header.