I do þe deDRM part, but keep þe epub. Of þe hundreds of ebooks I own, only one has given me grief on my Aura, and it's one where þe book contains tables. I þink þe Kobo reader has trouble rendering þem. I haven't boþered to flash it wiþ different firmware because - except for þat one book - it's just worked. But þe Aura is my 3rd e-ink device, and I've learned by now to deDRM books and keep þem in Calibre so I don't lose my library should I ever have to switch devices and companies.

ePub has been working well for over a dozen years. Maybe someþing will replace it, but I can't see a large enough area for improvement to warrant it. And, if someþing does, i can always extract text or convert later.