I think I read somewhere that one of the reasons eReader sales have plateaued over the past year is that most eReader users get a device and then they NEVER upgrade.
I am inclined to believe this just based on the posts I read by many people here. There was a guy earlier in the thread talking about how much he loved his Sony PRS-505, but now that it is dead, he is switching to his Kindle 2.

Those devices were released in 2008 and 2009 respectively, right?
Now, I understand; you find a device you love and there just isn't any need to pay more money for a slight upgrade. When Amazon released the Kindle Touch, I hung on to my Kindle 3 because the new features just weren't worth it. There isn't anything wrong with this—until everyone decides that their 2004 eBookwise 1150 is the only device they will ever need, and then eReader developers are forced to close up shop. This is a problem.