My dad has a Sony e-reader that he loves. He uses it almost exclusively for out-of-print public domain books and manuscripts that he gets from Google and other sources, mostly as .pdfs.

I got one just like it for Christmas, and although I'm working my way through a stack of print books before I buy any e-books, I have to say I'm very disappointed that there's no option for backlighting. I need the same bright light to read my e-reader as I do for a print book. No reading on subways, buses, my living room at night, many hotels, etc., without carrying a book light too.