Almost worthless for me...
I was desperate to find an e-ink device with pinch-to-zoom, so I jumped on this as soon as I knew of it. Now I'm sorry I did. The device does work at the simplest level, but press it in any way and it falls to pieces. I took my standard set of ebooks (all PDFs) I use daily in my NookColor that is contained on a 32GB MicroSD and loaded it into the Sony. Almost immediately the (already slow) device went pretty much dead. Opening the list of books either takes 10-15 minutes (no, I'm not exaggerating) or completely locks up. Pressing reset does nothing. Pressing the on/off switch brings up a screen asking if I really want to shutdown and when I select "Yes", it freezes again. I frequently get a message saying "The ContentManager has stopped working". This message is displayed in response to my attempt to enter three different "modules". After a hour of trying, I gave up on trying to do anything with the reader with a large microSD installed, it just can't handle it. After giving up on the microSD I removed the card and rebooted (waiting another 5 minutes). I then opened the preinstalled Jules Verne novel and got to see page one, and the reader locked up again. Reboot again, wait some more, try a different preinstalled book, ok, this one opens without crashing, whoopee! I finally get to try the pinch to zoom, and yes it does work, but it's very clumsy and difficult to use. Partially this is unavoidable, since the screen is e-ink, there is no feedback to see the size change as you pinch. My biggest complaint here is that the resize is slow and repaints the screen twice when you finish your resize (once apparently is a simple pixel zoom and the second time actually re-renders the fonts). Why would they do something so stupid? Beats me. I could go on and on with my experiences, but I'll just skip to the conclusion.
Conclusion: An acceptable reader that is similar to the Kindle graphite model but is far less polished. Crashes frequently, hangs mysteriously, overall the firmware is a fiasco. Although the pinch to zoom feature should make this device far nicer to use than a Kindle, poor execution leaves it as a device that should be avoided.
Since I've now used most of the major ereaders, some people might like to know of ereaders that I would recommend. I use the NookColor most of the time, it is a very good reading system, but does crash occasionally, and battery life is typical of an LCD system, so power needs to be available regularly. The Kindle DX has an excellent screen and will last a very long time on a charge. The DX is awkward to navigate for large format PDFs, but the screen is large enough that this isn't too much of an issue. The standard Kindle graphite 6 inch is acceptable, but only for simple fiction, not formatted text books. The iPad is a good reading device, but is too large and heavy for my taste. The MacBook Air isn't really a reader, but is small enough and much more convenient to use than the iPad.