I got my other half Sony's 2nd generation "pocket" reader (the PRS-350, released in 2010) ages ago, and after getting used to the "screen wipe" effect on page changes she became quite attached to it. Compared to the PRS-300 I got ages ago it's noticeably lighter and the "Pearl" type e-ink screen has better contrast, and a nice feature is being able to change the page mode to "margin cut" to maximise use of space. Should you want to change the embedded default fonts it's supported by boroda's custom firmware hacks, and of course you can manage books with Calibre. The touchscreen is simpler to use than a cursor for things like selecting words to look up in a dictionary (several are included, but you can't add your own) and quickly choosing menu items, and a couple of gigs of storage is provided. A touchscreen also feels more natural for page turns, provided you either use a stylus or are very careful to avoid gouging it with fingernails. I may get one eventually.
More recently, before Amazon announced the Fire tablet and the new basic model Kindle, I picked up a Kindle 3 (now officially called the Kindle Keyboard) which, like the PRS-350, also has a Pearl-generation e-ink device but with a larger 6" screen. Plus points are that you can add translation dictionaries, the control over font size / font family / line spacing / orientation is comprehensive, and it allows you to read whilst charging. You can also claw back even more screen area by editing HORIZONTAL_MARGIN in \system\com.amazon.ebook.booklet.reader\reader.pref and restarting the device, although you need to make sure you don't have a book open whilst doing this or the setting won't stick.
There are enough niggles that I'm not as keen as on the Sony devices, mostly things that wouldn't bother the average user. It won't allow you to group books into categories unless paired with an Amazon account, it doesn't show a battery indicator whilst you're reading, and it doesn't let you customise the screensaver without hacks -- so you're initially stuck with random pictures of authors and fish. I don't see much point to having a screensaver on an e-ink screen, or if there has to be one then the option to use the cover of the current book is a blatantly missed opportunity. It's very much a walled garden experience, basically. And for a device on which you might reasonably want to skip ahead to a numerical position on, it seems stupid the keyboard is letters only.
Of course, what I really want in a consumer-priced reader is a touchscreen colour e-ink model with a large screen. That could be a while coming, given that current focus is on backlit tablets, although the education-oriented Ectaco jetBook is a sign that we're slowly getting there. Triton screens, whilst apparently rather slow at the moment, are already providing newsprint quality reproduction in colour.
 A quick trip to http://www.kubizo.com/changing-kindle-screensaver/ and some messing around in XnView and I was able to set up the Doctor Mew series by Jenny Parks as screensavers with minimal fuss.
 This can be turned off if you want to use the Kindle for something like displaying sheet music by typing ;debugOn [enter] into the search box, followed by ~disableScreensaver [enter]. ~resumeScreensaver to turn it back on again and allow the device to sleep.