Phat said: "I'm still kinda looking at the bookeen. it seems to be about the lightest one - at 6 oz, I'd definately take it in a backpack."

Arguably the lightest solution is to get a multi-purpose device. I know that what constitutes an acceptable reading device varies by the individual, but I'm happy reading books on my smartphone, which has a 1.75" x 2.25" screen. This is much less than any dedicated book reader I think, but with cheap and light drug store reading glasses I quickly forget the medium and get lost in what I'm reading. As this device is also my cellphone, GPS, voice recorder, at-need MP3 player, and journaling device, it comes out very lightweight indeed on a per-function basis.

No question, however, that the bookeen or any dedicated reader will make for a more pleasant reading experience, I can only say that the smaller screen works fine for me.