My ipad arrived two days ago. Thus far I am very pleased with my new toy. I haven't had too much time to mess around with the ibooks program but I'll have a full report asap. One thing I like about it is that it has apps for the kindle and Barnes and Noble.
Here is an article from the New York Times comparing various e-readers. The author is Joanna Stern, a technology journalist and an editor over at Engadget.