I just install this firmware last night, I have to say, much better than the original (at least for my usage).
For a while now, I've been trying to add Unicode hack to the Kindle2 and without a success. I read a lot of Chinese Novels, mostly I read them on my phone but the battery runs out fast. Kindle2 uses less energy and for that reason alone can be important for me. However, no Unicode compatibility means that I have to load the Chinese text into Words and then print it out as PDF, it was the only way I found to read Chinese on Kindle2, well until last night! Thanks OP!
I waited for Amazon to update the K2 firmware 2.5.8 but it hasn't change for months (if not years). Anyway, this firmware allowed me to load book.txt directly without a problem. The neat thing is it read back to me in Chinese too, not that I need it, but it's cool. The page advance is faster than original firmware too. This firmware runs on top of the Kindle original firmware, so you can switch it back original if you want. Duokan has features for reading, playing MP3 and pictures, but no experimental browser. It would be neat if it can has one, so I can check my email at times. But I got my phone to do that, so not really need it.
Now for those longer gaps I can use Kindle2 to read and leave phone to do phone's thing :-)