As an Apple fanboy, I can absolutely confirm that there is a problem with text rendering on the iPad. For example, I have an alu unibody Macbook 13 -- whose pixel density is about 30% lower -- that is much clearer and easier on the eyes for reading text.
I suspect this is just a software problem with the rendering strategy, and can be worked out. It's acceptable as a reader, but nowhere near what it could, or should be.
I read about 800-1000 pages a week for my work, and I just can't get through it all on the iPad -- too exhausting. I put most of it on a Sony 505 reader for an efficient and painless reading experience.
My experience is just the opposite. The text in Safari and iBooks is fine on my iPad, but on my latest gen 13" MBP, it is HORRIBLE!!! It is blurry, jagged!!!
I wear reading glasses. Not very strong, however. 1.0 in one eye, and 0 in the other. When I put on my reading glasses, the text on the 13" MBP is just horrible! I have OS X 10.6.4 and Safari 5. Before the update, in 10.6.3 and Safari 4', the text SEEMS a little bit sharper!
I was blaming the low res of the 13" MBP--1200x800, but it seems that there is another possible cause to the problem--sub-pixel rendering.
The text on the iPad seems to be fine, when I put on the reading glasses.