Kobo should really announce the correct firmware version in future updates, even if all there is are minor bug fixes, doing it otherwise doesn't look "serious", I don't know.
I'm very happy so far with 2.1.5, turning pages is fast and finally I have a Spanish dictionary, awesome!
BTW, I was testing a manga in cbr and it looks kinda small, if I turn the images to landscape mode, it's a little difficult to browse the pages. Any advice for this? Do you use your kobo to read manga?