It still suffers from the same old problems the handhelds suffered from 20 or so years ago. Sure the optical tracking got better (optical mouse ftw) but books and paper are elastic things so there are bound to be distortions. And those can be fixed with software only so well and it interferes with OCR.
You can take a digital camera to the library. If the library also provides a good reading light you might end up with a better result with less fiddling a mini scanner across a page and never knowing if it really got everything.