A question I've heard since the iPad announcement: "So when are you giving up your Kindle and getting an iPad instead?" How about never? I may eventually get an iPad or a similar device for mobile media, but the Kindle is a dedicated reader device and the iPad is not.
Joe, however, is apparently frustrated enough to change platforms. I'm not sure what his distress is about when he says: "The device's functionality is pretty much the same as it was when it launched more than 2 years ago." Yes, it is pretty much the same -- it's an ebook reader, not a media hub. The Kindle delivers on one promise: an excellent reading experience. It does not promise social networking, sports scores, Twitter integration, or anything beyond books. That may very well change, especially if Amazon wants to keep pace with Apple's competition.
Nevertheless, getting angry at the Kindle for a "lack of innovation" at this point is rather like getting angry at a hardcover novel for not including a fold-out map of the USA, a crossword puzzle section, and a coloring book. The novel does not promise extraneous features; neither does the Kindle, beyond the experimental (read: weak) web browser and Mp3/audiobook functionality.