I've been reading eBooks for about ... 11 yeas, on the tiny screens of my PDA/windowsphone/smartphone/iphone/ipad/s3 and occasionally on the monitor, etc.
the screen size has improved immensely though. perhaps to offset some hyperfocal blindness of reading white characters on a black background on a 3" screen.
its a lot easier on the iPad, the back light on the screen helps, and the smaller dimensions really places emphasis on the tiny interface.
mostly i end up reading to do something while trying to fall asleep, and then read for 4-6 hours, so not quite a preferable option ... sigh.
i also tried switching to audio-books, which gave me a similar sort of insomnia,
but the chapters get out of sync pretty fast when the .... words ... thing, as she walks through ... out the door... zzz ... and that's the conclusion of war and peace part 1, thank-you from audible (sic)
The biggest headache with using a kindle is that the process is kind of broken here in Australia,
i can't use amazon or audible to download the books here (Global zone restrictions apply to everywhere outside US/UK in Australia) ,
so i use the "Other" internet to get books. the upside is, you get thousands of books, the downside is time, you end up spending more time organising thousands and thousands of books because they all come in these bulk packages (top 15,000 nyt bestsellers ... sic)
i have used the eink models, and the tablets, and have bought both for other people to get the hang of, and preloaded books on kindles before.
i personally kind of like the paperwhite kindle, but you do have to get used to the display, and nighttime reading, being as it is, the ipad works really well, lots of spacing, and you can contrast flip the backdrop which makes reading easier, not so much battery life, but everything else is good. ie. you can read half a book, and then you have to charge it for 2 hours. same with an audiobook on an iphone, you get about 8-12 hours and then the battery needs attention. so the kindle makes a big difference if you're travelling around, you don't need the bulky battery packs.