See my review
EZ Reader: Initial Impression, where I agree that the Hanlin only has good support for FB2, RTF (no images) and MOBI. I did not try TXT, but it apparently also invokes CRengine (the library at the heart of CoolReader) like FB2 and RTF. I have not seen a Cybook, but I'm sure its MOBI support is better than the Hanlin's. The Hanlin's FB2 support may be on par with the Cybook's MOBI though. CRengine also apparently supports HTML, and EPUB - but these formats are not currently using CRengine on the Hanlins.
If you have a large library of ebooks, the Hanlin's folder (directory) support is a big plus.