Naomi S. Baron has released the findings of a survey comparing use of e-reader devices to printed books. These findings corroborate with similar studies, which consistently show that readers of printed books have better concentration levels, and retain more of what they read than those using e-readers.
At work we have an iPad as a way of encouraging students to use our ebook platform, and I also recently bought one of my own. I went to town loading it up with some free and public domain ebooks, such as F. Scott Fitzgerald's The Great Gatsby and Charles Dickens's Great Expectations.
I may or may not download some non fiction titles as well, because I prefer to read them more carefully. The irony comes from me using the internet to express the opinion that it's better to read in print than online. What do you prefer?