Yes, be very careful of them.
I was surprised how attached I had become to it and how often I still reach for the ereader
And that is after only 2 months! I find it harder to go without than an MP3 player but I suspect that depends on how you are wired.
Now that I have read eink I can't go back to regular books and refuse to buy a book until I get a new ereader. That leaves me reading a fitness book that I have been meaning to read for years, ahhhh save me!