regarding eReaders and sleep

I've been using my laptop to read .pdf books for a while but I found it screwed up my ability to sleep, so I've stopped, and am now considering an eReader instead. So, to those who have eReaders, which one do you have? Do you like it? Do you use it to read before bed, and do you think it affects your quality of sleep? I'm obviously looking for one that doesn't have a backlight or at least has settings to turn it off.