I am using my Cybook for exactly 8 weeks now, which means I have taken it to work exactly 36 times.
While traveling I always have it in my backpack, between a (paper) notebook and my lunchbox, inside its (very nice) black cover.
So far, so good, but with only two months of use there can't be said much about the durability of course.
The software is rather good, I have had 3 or 4 freezes, 2 with PDF's the old firmware couldn't handle (so they don't really count) and two with the new firmware after a 'full-charge' of the battery (where have we heard that story before?

).
At the moment my conclusion is that ,with normal care, the Cybook is well apt to its task. I hope I still can say the same a year from now