If you're wondering if Eberronicon is useful, yes. Purchase it before you buy any other material if you're new to the setting, and purchase it if you have all of the other material and want a concise way to navigate it.
My experience before using this product: I developed an interest in Eberron about a year ago. Since then I've tried to absorb all of the material I could find. That means all of the source books and adventures from two editions, archived Dragonshard articles, KB's articles on his website, the Manifest Zone podcast, some ok YouTube videos, and even the few 'ok" comics that were put out.
I started DM'ing two 5E Eberron games once I felt like I had a basic grasp of the setting. My players were new to Eberron and needed/wanted a more comprehensive introduction so they could understand the differences between in other settings where the world was less of a character and more scenery. So I spent time preparing to answer possible questions, or coming back during later sessions to explain things, or looking things up we all wanted to know at the time. Not impossible with a folder full of searchable PDF's, but a long enough side bar to detract from the session.
Eberronicon has served me in two ways. If my players have a question about a specific person, place or thing, I can read them a succint entry that it would have taken me much more time to cross reference. And when I'm researching for the game etc., I utilize it's true power. It functions as an Index in that it provides footnotes and links to the source books and articles from which the entries were derived. If I want to find anything, it is the first document I open.
It is well organized, comprehensive, and regularly updated with error corrections.
Worth every penny at full price.