As I wrote earlier, the documentation on the App was released some weeks ago, and now the App is released itself.
Install it in your SPO tenant and play around with it (if you’re unhappy with the existing relevance or if you want to test it out).
I’ll test it out in the days to come and try to give a step-by-step review on how to use it. David Hollembaek and I will also demonstrate how to use it at SPC in “Managing Search Relevance in SharePoint 2013”.
