Everyone would have preferred that kepub and epub were as alike as possible in 2.0. I believe that they ran into some delays and thus out of time before the deadline for the release in Japan. In a perfect world, this would not happen, but it is not a perfect world.
As end users, we see only what we use ourselves. We don't see what what has to happen on the development end to make things happen. Let me give you an example. Many of us know that there is a new ePUB standard, ePUB 3. Among other things, ePUB 3 addresses the needs that certain languages (including Japanese) have to be read up and down, rather than from side to side. Adobe has been working on becoming ePUB 3 compliant for a long time. They aren't there yet. We can download and run a beta version of ADE, but it is not ready for release. Equally important, the mobile version that would let Adobe ePUB3s run on devices like the Kobo Touch is not ready either.
Kobo has to wait for Adobe to do its thing before they can handle ePUB3 files/books on the Touch. They did not have to wait for Adobe to handle ePUB3 for the kepubs.
(Note: the ePUB issues we are currently seeing have nothing to do with ePUB3.)
What they did have to do though was implement a different backend for this to happen. During the four months we were waiting for an update, that is exactly what they did. Kobo implemented
ACCESS NetFront(TM) as the EPUB 3 Standard viewer engine for the non-Adobe services they run. This would include the Touch, the various mobile device apps, and the new web based reader app to be ePUB3 compliant and ready for the new features it offers.
This was a very big deal. I believe it is also is why the kepub format got more and earlier attention in this release.
Earlier in Kobo's (fairly brief) history, ePUB development always seemed to lag behind that of kepub. That has not been routinely true for awhile. What has been true is that from the beginning they have had two different development environments to work in. I imagine the decision to do this, rather than to do something like Sony did and only work within the Adobe environment, was in part financial. Adobe charges each time those acsm downloads happen. They charge for a bunch of things. It also means waiting on Adobe for things like ePUB3.
I don't have any idea exactly what the developers are working on right now, other than to say that they are working through a list of known issues and problems with the firmware.
Font tuning is a big step forward, but it has to be properly implemented, and it missed the mark for ePUBs. Something having to do with the different backends/development environments seems to have screwed with sideloaded fonts on ePUBs as well. And somehow, the font sets we did have changed (and not in a good way).
Bookshelves are also a big deal. I believe what was released is first step in a longer process of making that feature better and more useful. This is an area where ePUB and Kepub diverge. A big part of this seems to be the reality of Kobo not being able to sync things having to do with sideloaded books through their server--a privacy issue in Canada. I imagine there will be some sort of workaround, but I don't necessarily think it will happen as quickly as we would like. If the Kobo driver work for Calibre happens, then this may solve some of the issues for those people who use Calibre. It's a stop-gap measure, but it will be helpful to those folks who use Calibre for library management.
None of this really explains why things like the slow page turns on ePUBs weren't addressed before the release of 2.0. It's hugely annoying, and presumable not a difficult thing to fix. FWIW, the last beta the beta group saw before release had slow page turning for kepub and epub books. Kobo uses the beta group to develop a list of known issues, but the group doesn't necessarily see them addressed as part of the external beta testing process.
This has been a long post; it's so long that I should probably give Karma to anyone who makes it all the way through it
. Notice that throughout the post I used phrases like "I think", "it seems", and "I believe". This was intentional. No one from Kobo sat down over coffee with me and put this all together just like this. It's more than guessing and less than perfect knowledge from the horse's mouth.