I'm kind of sad to see these devices fall off the market, though I can't say I didn't see it coming. They closed their "Sony Reader Store" for ebooks on the 20th of March, and sent another email detailing how to switch to Kobo. I've had a PRS-T1 for years now, and I love it. It's got a super nice feature where you could long-press a word you don't know and it would show you its meaning on its internal dictionary, or you could try searching google and wikipedia for it (if you were connected to wifi). It's so handy that when I switch back to regular books after a couple sessions with my ereader, I find myself trying to look up words in regular books by putting my finger on them. With the wifi off (or set to standby), the device supposedly will go for a month of regular (read: three or four hours daily) use. Never tested it, but boy it was nice, especially in an era of charge-nightly smartphones.
By far the best feature was that my PRS-T1 seems to be perfectly sized for my hand. I can hold it in my left hand and swipe the screen (to change pages) with my thumb, comfortably. Combined with the fact that it only weighs a couple of ounces, and it's actually possible to do extremely comfortable one-handed reading. I should go plug in the thing. And find more books for it. And read more.