My mum's Sony story - she got a Sony ereader and loved it. More choice of formats (IIRC) and better support from local library. However, after a couple of years, it stopped holding a charge. Accepting it was out of warranty, she returned to the Sony shoppe, where one of the "experts" (still PMSL) told her the battery was gubbed and she would have to buy a new ereader because the battery in integral to the circuit board and cannot be replaced. Obviously not happy with this and with the thought that she might have to buy another one in another couple of years, she bought a Kobo, more later. that wasn't as good as the Sony in terme of support from the library, something to do with digital rights which allow the library to send you a book which will self-delete after a couple of weeks. She was moaning to me about it, I said that (the "expert"/battery bit) sounded like bollocks and to give me the Sony. Lo and behold, a huge number of screws, and UNCLIP the batery and CLIP IN the new one (£20 IIRC) and woohoo, working Sony. gave her it back, she's happy. She gave me the Kobe because she doesn't use it anymore. So battery issues notwithstanding the Sony seems to be pretty good, and you never know, you might pick up a cheapie that just needs a new battery.
I've never really wanted an ereader, but now I have the Kobe, I like it. The page quality is excellent, so is the battery life. The screen has a few light marks on it, so may be fragile, but a couple of quid on a case should protect it. In epub you can't magnify images (I'm ereading Game of Thrones and there are maps of Westeros that are difficult to read, so zooming in would be useful). Also, no backlight, good for battery life, but crap for reading in bed at night. Case bought from Amazon was about £10 and came with clip on light, bulky but ok.
EDIT - and I understand that you can use non-Kindle readers to read kindle books bought from Amazon, bit it's a bit of faff.