I've tried 3 different E-book readers: The sony PRS505, the Kindle and the iRex iLiad. In the end, I returned the kindle and gave the 505 to my dad and kept the iRex. The main reason was that the Kindle screen was WAYYY TOO SMALLL to read full sized Pdfs and academic journals.
The sony had the same screen-size problem as the Kindle but its cheaper and it was a good fit for my dad, who mainly reads fiction books. The iRex was the keeper because of its big 8 inch screen.
The new kindle 2 seems to have the same screen size as the previous one, so this is an absolute no-buy for me. However, the upcoming plastic logic reader looks promising with its full A4 sized screen and could be a good fit for me.