If it's e-ink technology,the price will be closer to $1000 than to $100!
I guess it'll be around a $700 initial street price,going down after that.
If it's reflective LCD technology, I expect a device like this to cost around 200-250 bucks street price.
Battery life will be interesting, and also if they are going to provide the device with a flexible frame too!
I'm not so for flexible devices, they are only good for not breaking when you have it packed in a book bag, but I wouldn't want a device like this to be too flexible like for instance silicone or so... I do hope it still retains some sort of stiffness, and that the stainless steel back won't feel too cold.
Battery life, processor speed, page turn speed, file type recognition, and info on extra feats (like wifi, 3G, audio playback,etc..) are perhaps pretty interesting to know when the device comes out!