[Ken Maltby]

Actually, you can purchase .epub ebooks, without DRM, from anyone that sells them. You can purchase epubs with DRM and remove the DRM then read them on your AuraHD.
Just not by WiFi through an account associated with your device, on your Kobo.

And - You can add alternative readers to your AuraHD and buy and read many formats including epubs. (Like I do.) Since both of the alternatives can read from "hidden folders", you can avoid the processing of a large ebook library, by the Kobo software. If the Kobo software is not managing all your books in its database, there are fewer chances that the database will become corrupted.

The AuraHD is like a great monitor and video card combination in a well powered PC setup. You are getting the best image quality, but maybe some of the rest of the PC is not so hot. Now for ereading the image of the page is the most important thing, IMHO.
The rest can be improved/fixed with new firmware and/or software, also other alternatives are both available and being developed, all the time. There are even some working to have the hardware run under Android and other Linux OS.

Luck;
Ken