This is an article with the obvious and some nonsense:
Baron was surprised by the results to the question of whether students were more likely to multitask in hard copy (1 percent) vs. reading on-screen (90 percent). "When a digital device has an Internet connection, it's hard to resist the temptation to jump ship."
Not if it's a real eReader with eInk type screen. However the trial of Kindle DX for University Students was a failure. That's why the Kindle DXG is available cheap on amazon.com for International Shipping. Totally stupid research. Reading on a Laptop / Tablet / Big phone is an eReader Application at best, not an actual eReader. Thus Kindle Fire is more a Tablet and not a true eReader. Free Wikipedia and 60 Mbyte free everything else on a Kindle DXG isn't a distraction unless you are a digital masochist!
Random access is rubbish on all digital devices. I analysed this and came up with solutions in 1988-1989 that no-one has implemented yet.
PDFs are useless on screen unless your screen can display full page at 200 dpi+ resolution with shades (anti-alaised) or 300dpi+ if not.
LCD and AMOLED etc are only good for photos, video and not prolonged reading. The eInk is only screen tech close to paper for reading experience and the User Interfaces are poor.
Web pages are a misnomer. They generally ignore invention of the Book about 2000 years ago (Codex instead of Scrolls). Scrolling is the pits.
Document organisation is abysmal on the Kindle or Sony PRC.
So the problem isn't eReaders inherently, but you need to have passive screen only (eInk, or perhaps Mirasol. The Chinese eInk clone is like 1st gen eInk on original Sony PRC, Bookeen and first Kindle. The "official" eInk tech is now very good (used in 5th Gen Kindle Touch that came out after the 2nd version of paperwhite). The Kindle GUI software is still very poor. But nothing on a Tablet or PC is better, not even the best PDF readers on screens big enough to simulate the printed page. PDFs are for print. The problem is you need a 2400 x 1800 portrait 12" high screen, ideally eInk for PDFs and better GUI and Library than Adobe or Foxit suppplies on OS X, Windows, iOS, Linux, Android or Kindle has.
The Kindle DXG is nearly big enough for PDFs, but the screen isn't high enough resolution. The regular 6" Kindle though is fine for real ebooks that are not text books, just novels read sequentially.
I've just marked up nearly 600 notes on a 130K text I wrote on the Kindle and it's nearly rubbish for review of them as it can't remember location on Notes pages and the clippings.txt you can copy to PC only has the notes and not context. The Kindle locations are only meaningful on the Kindle. They seem to be roughly 11 to 12 words long. So if the Kindle powers off, unlike a book, it's back on the first page of the notes (6 per page!).
On the Kindle even when there is no DRM (i.e. your own text or Gutenberg) you can only copy / quote short extracts and only to Twitter or Facebook! Daft!
I still think the eInk Kindles are best thing for reading invented since printing press. I want to get a 6" touch to complement my DXG. The Fire is pointless except for Amazon integration as it's a Tablet. I'd rather pay extra and have a generic tablet, but as don't go anywhere I don't need a Tablet. The laptop is fine (I do actually have a 7" tablet and a large Android phone)
Summary
The regular real eInk screen dedicated eReaders are OK for fiction/novels, FAR better than tablet / PC for Gutenberg or saving paper proof reading your own work (or beta reading another author). They and tablets/laptops are nearly useless for text or reference books.
I prefer to get real books.
Only the large kindle DXG is at all any use for PDF docs etc, it can be some use for short reference material (1 to 10 pages) or scanned text books out of print. Printed text books are better. No decent eReader can do colour. The only tech that MIGHT do colour for real eReaders is the Qualcomm Mirasol, but it seems to be close to vapour ware. LCD and LED / AMOLED etc are inherently unsuitable.
The Library management, random page access, general GUI, lack of copy/paste, inflexible annotation and software generally of eReaders (dedicated or on Tablets/Laptops etc) is frankly ignoring all 1970s and later research. Hacked versions of Linux/Windows/Android as OS and customised Mobi Reader originally on palm Pilot! Pathetic!