I would also recommend Hanlin/Bebook/Astak (same hardware, different logo on the front) or a Sony reader.
Pro for Hanlin: It supports (AFAIK) more formats than the Sony.
Multiple firmwares, you can use the one best suited for you.
Contra(?) for Hanlin: I don't know how does it manage DRMed books, if you intent to read such.
Pro for Sony: With the price war going on, it's cheaper than H/B/A. Make sure to check the package contents though - there are some opinions, that buying an Astak with all the extras is cheaper than buying a cheaper reader without them, and then buying the extras out of necessity (cover for example).
Also pro are the Sony store and the touch screen (if you want one, of course).
Contra for Sony: Formant support.
I'm not sure if someone mentioned it already, but you could use the site
wiki and compare all readers without direct connection to the stores. You will find it in the
"Other Interfaces" row.