I just purchased my 3rd eInk based ebook reader, a Kindle Paperwhite. Previously I owned a Sony PRS-505, then a Nook Simple Touch. Between the Nook and the Kindle, I've been using a Nexus 7 tablet with Mantano reader (I also played with Moon+ reader for a while).
I switched to the Nexus for two reasons - one, I find that I want to read in the dark FAR more often than I want to read in full sun, so an LCD screen made sense at the time for that reason. Two, I figured it'd be nice to have a device that I could use to browse the web, check email, play games, etc.
I felt that the screen on the Nexus 7 was fine for reading.
I'm switching back to eInk primarily BECAUSE the Nexus 7 can do so much - I found that if I had a few minutes, I would play games instead of reading, and as a result I was not getting nearly the amount of reading done that I really wanted to. After switching, I'm also finding that apparently I've been fooling myself about the LCD screen - it's not nearly as nice to read as the eink. I find myself reading for much longer at a stretch, an hour or two instead of 10 minutes.
Regarding the device itself, I think it's very close to being the perfect thing. It's extremely light, the battery is said to last for weeks, the built-in light is completely perfect - absolutely uniform and extremely adjustable from barely on to as bright as it needs to be (if you need it brighter than that, then the room is bright enough that you don't need it at all).
I have a bunch of ebook content already and I am having no trouble loading it on the Kindle. All of my existing content is in Calibre, some purchased from Baen (with no DRM), some from Google Play (with DRM stripped via Calibre plugins), some purchased from Humble bundles or other non-DRM sources, downloaded from Gutenberg or MobileRead, etc. The Kindle is automatically recognized by Calibre when I plug it in, and I can just drag stuff to the "device" icon to load it. I can also hit my Calibre server using the Kindle's built-in browser from anywhere, find a book, click on the "mobi" tag and it just loads up. I do have to be sure that I've got Mobi versions of what I want, but that was easily taken care of by hitting "select all" and "bulk convert" and letting it run overnight.
I did also load a book from the Kindle store - a copy of "The DaVinci Code" that was free this week, giving me something to try loading directly. I also was able to pull it into Kindle for PC and then drag it into Calibre, which took care of the DRM for me with not even a notification. Perfect.
I finished a book I had been reading, then read an entire book on it Saturday, and have started a third. At this point I have to concur with the guys at Tested.com - Amazon is always improving their product, but at this point, I don't know what they could even improve on the Paperwhite. Sure, the page turns are not instantaneous, but they're plenty fast. The backlight is perfect. The battery life is extreme already. It's very, very light. Unless they come out with color eInk, I think they may have perfected the ebook reader.