I think the main positive thing is you get a _second_ renderer! (Without having to install Koreader, Coolreader, Plato, etc.).
For me, that creates quite a lot of ebooks (for myself, mainly because I want to read a lot of stuff on the best reading device I got, but also because I find it a bit fun), when I want to do some feature, I google and read how you can do it, when I look in the ade-renderer, it rarely support the feature, but the kepub-renderer almost always does.
For me, that is a really big advantage.
(Side comment, now with my new Pocketbook I'm back to find other solutions.... arghh.... I see a Forma in my future.
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