As mentioned in a recent post, my wife bought me a Sony PRS-500 Reader, and I like it a lot. I've just found out about an upgrade offer: PRS-500 owners can trade in their readers for discount on a Reader Pocket or Reader Touch. The offer expires April 10, 2010.
(Bummer. Turns out that I have a PRS-505, not a PRS-500, so I'm not eligible for the upgrade. So I guess I'll just have to wait for the Apple tablet.)