Gave it a spin last night - I must say that I didn't have very high expectations, but Duokan Lite is surprisingly rather damn good. It's a lot faster in regards to UI actions, page turns are near instant and it has some basic options that the vanilla firmware is missing (i.e date config, easy font addition and switching).
Some of the UI is too cramped for the translated strings, other areas have a few grammatical errors or arnt translated at all. The EPUB/reader seems to reformat things a bit too much, but it's largely usable. The progress bar being in the lowest visible pixels is somewhat of a strange choice.
I'd love to play around with some of the code - but it seems to be a commercial venture and I'm not seeing a public repo (which is odd, I assume there's at least some of the kindle gpl infested stuff in there - but perhaps not). But for now they seem to be working quickly and in the right direction.
In all - I'll be keeping a close eye on it