I've come across a bunch of articles on this topic; I almost wrote one myself. But I'm not so sure the market is over saturated; I'm not going to jump to the same conclusion as everyone else.
But I do think buyers should be cautious. I wouldn't buy a device that is dependent on a service (sorry, txtr). I wouldn't buy an ereader that is dependent on a locked in format (Jetbook Lite, eSlick). And I wouldn't plan on being able to use the wirelss connection of an e-reader; if (when) Irex shuts its doors, will Sprint continue to support the DR800SG?
And in case you're wondering why I don't include the Kindle in the above, it's because Amazon is the 800 pound gorilla. They're not going away.
CES: E-readers' next chapter might not have happy ending (CNet)
The e-book wars of 2010: displays and hardware (Ars Technica)
Too Many eReaders (Gawker)
CES is Not a Book Fair (Publishing Perspectives)
"Deluge" of devices threatens e-market (the Bookseller)