I didn't actually cover this in the article but it's probably worth addressing here. To answer your first question about do we know how effective it is, the answer is kind of in the sense that everyone I know in the industry who has implemented this for themselves and for clients has seen positive results without any exceptions (that I know of).

I know that doesn't make it a FACT (though it's extremely compelling in my books) but no one outside of Google can actually provide you with the true numbers needed to answer the question unfortunately.

But to address the second point about why every SEO person is losing their mind about Authorship, it's to do with more of a long term play. The general consensus at the moment in the industry is that Google is desperately trying to move further and further away from signals that are more easily manipulated than things such as links.

As a result you have things like Google+ and Authorship coming into play, and even if they aren't officially ranking signals RIGHT NOW it's almost a certainty that that won't always be the case. The reason why this is so important though: it's fairly rare in SEO that you get many chances to get a massive head start on your competitors by becoming an early adopter of some technology, this however is looking like it is going to be one of those times.

So it all comes down to the fact of, when the day comes where they DO contribute to rankings and you decide that you need to do it anyways, do you want to be starting from scratch or do you want to know that you already put a year or two into building up what they consider to be an authoritative authorship profile?