In the meantime I just downloaded a DRM free sample from the Kobo store. Yeah, I rather deal with a dedicated software to download than with credit cards but maybe that's just me.
The interesting thing is that you get much higher quality pictures within the Epub than from the same book and Azw (I guess it was 3 as well) from the Kindle store. So Epub over Kindle definitely worths it, for me, even if it is more expensive by a whopping 3-5%!
Thanks for your feedback.