This year I finally bought an e-reader: a "Kobo Libra H2O": a 7" 300ppi screen with an adjustable colour temperature front light, waterproof, physical buttons on a "margin"/spine which pushes the case dimensions up to 8", which is sadly a little too big for most jeans pockets.
In fact this is the second time I've bought one. Sarah and I bought a pair of Amazon Kindle Paperwhite (2nd generation) readers as Honeymoon gifts for each other in 2013. Sarah took to hers, but after giving mine a try and reading a couple of books on it I ended up giving it to my Father-in-law.
The main problem I had with it was the colour temperature of the backlight: it was too blue and "clinical". It's interesting to me to realise how the environment that I read in can become indelibly linked to the memory of that book. One book in particular that I read on the Kindle was James Smythe's "The Machine", a modern twist on a classic horror story. This was perfectly complemented by the somewhat pallid, sick colour of the backlight, especially on its lowest brightness settings. It didn't go so well with other stories.
I got on much better with the Libra H2O. For me, e-books and e-reading has not replaced traditional paper books, but complemented them, giving me an opportunity to read in contexts and situations where I couldn't manage with a real book (such as in the pitch black, lying on my back with a toddler on my chest). I feel that being able to read more often thanks to the e-reader has spurred me on to read even paper books more frequently as well.
Unfortunately the screen broke, about 10 months after I bought it! After a bit of soul-searching on what to do about replacing it, and briefly considering the latest Amazon Paperwhite (which now has a 300ppi display and adjustable-colour temperature front-light). This looks like a very nice e-reader: no physical buttons which is a bit of a shame but narrower without the margin/spine of the Kobo, so possibly more pocket-friendly. On the other hand, I really felt that I wanted to avoid giving Amazon the money, for a whole variety of reasons.
So I instead settled on the "Kobo Libra 2", which is a slight refresh of the Libra H2O, but almost identical. I'm going to pair it with a nice cover for when its not in use and hopefully it will last longer than its predecessor.
My current favourite feature on the Libra 2, that I don't remember on the H2O and I'm fairly sure doesn't exist on Kindles is it supports a "night mode", which is effectively a reverse video, white-on-black mode. This is fantastic for keeping the light levels down at night. I was already using the backlight at about 2% brightness and occasionally found even that too bright.