Overall the device does as it claims. The contrast is a little low, but in good, direct lighting it is acceptable. Shining a torch on it in a darkened room seems to work well, so I might consider getting a custom LED clip-on lamp. The screen refresh speed is OK, but it does take a few seconds between button presses - so you have to be patient.
Note taking is OK with the on screen keyboard and these can also be linked to individual pages of a book.
The reader works best with text documents, it can display comics, but the colour rendering in 8 greyscales makes it rather difficult to read. Converting them to black and white first is better. The page also needs to be the right size as panning is too slow.
The device has a nice screen size, though a little large to fit in a jacket pocket..
The Sony software supplied gives access to the device to manage books, notes etc, but is limited in its functionality and does not do any document conversion. The opensource Calibre provides more functionality to edit tags, convert between document types etc,.
My biggest complaint is with the categorisation of ebooks and the bookmarking / note taking functionality. There is only one "hot-link" back to the last book read, so if you are reading from multiple books, you will have to remember which ones they are, and definitely not useful for those sharing eReaders.
If you want something portable, lightweight and with a reasonable battery life, then this is the device, though you still can't beat a regular book - and it probably works out cheaper to stick with paper and check books out of a library.