I had the opportunity to take the Cybook on a 1 week vacation in the sun so though I'd add a quick update.
It worked great. The screen just got better in direct sunlight and I didn't have any heat related problems. You can obviously get some screen glare off the flat screen if you hold it in the wrong position but it wasn't a problem. We had some very windy days on the beach and it was great not worrying about pages blowing around.
It did rain almost every day but only for brief periods. I had a freezer bag along with me to protect it. There were periods where you'd get a drop every 15 seconds and I would have read a paper back in those conditions but decided not to expose the Cybook to it. The other concern was leaving the device unattended when off playing water volleyball or something. You don't worry about leaving a $10 pbook but I had to keep my eye on it. I already had this problem with my iPod though so it just increases the risk.
I was reading Ken Follett's "World Without End" before I left and was most of the way through it when I left. This is about a 1,000 page hard cover and I know that I would not have lugged it along with less then 200 pages left. It made the wait at the airport and the flight a lot better reading a book that I was well into rather then starting new and it was great finishing it on the beach the next day. I used to spend a ridiculous amount of time worrying about what books to take along on vacation and it was great to just pick up the Cybook and go. I also found it very comfortable to read while standing in the airport lines.
One odd thing that happened was I had it powered on going through the airport security and x-ray. For some reason it powered off but still had the text on the screen. I haven't had this happen before and it was fully charged. I pressed the power button once and it powered on and no further problems but it did give me a scare. I didn't think airport x-ray should have done this but I think I'll power it off from now on.
In short I'm still loving it like the day I bought it.
OK so I guess it wasn't a "quick update".
