I finally installed Duokan on my K2 (after the 2.5.7 update). I took the leap because
flip's site had the preconfigured English version available for download. His link is dated end of December and the last update on the first post of this thread looks like it is from November. I wanted to make sure I had the most up to date version.
Too soon to really comment on it. I like all the options in settings. Mobi files are okay. I've only tried one PDF (a cell phone manual) and it didn't seem to work any better than the original Kindle FW.
I'll play some more and come back with my questions.