I've had my Sony Reader for over a year and just got an Amazon Kindle about a month ago. Both have their advantages but I'm going to switch to the Kindle 100% after I finish reading the books I've already purchased on the Sony Reader.

The Sony Reader is smaller and I like the way you press the buttons for turning pages better. The Amazon Kindle is bigger and clunkier but has wireless delivery of books, magazines, and newspapers.

I ordered the Wall Street Journal on the Kindle and it's fantastic. I read it on my commute to work and actually find it easier to read than the physical newspaper. That might be unique to those who commute via public transportation because we have to learn "newspaper origami" in order to read the paper without disturbing our neighbors. I also like the fact that I can continue to get my subscription when I'm out of town (in the U.S., that is).

The Kindle also allows you to preview most books via download directly to the device, then if you like it you can just click to buy it and read the rest of the book.

Finally, I kinda feel that Amazon's committment to ebooks will be greater than Sony's and so feel more comfortable investing in a library there. With most books being DRM'ed, my use of the books I buy is linked with the company producing the reader.