I don't own a device but I follow these forums a bit and I'd like to take a shot to awnser your questions. If I say something stupid, I'm sure there's going to be someone correcting me
1) no search function yet, at least not content like. It'll be here soon. (I don't think I can say something wrong when I awnser it's going to be available 'soon'

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2) depends on how much you use the pen. I've heard numbers ranging from 7 to 14
3) you need as much light to read on the iliad as you would need for reading a book.
4) No it's not the new model. I don't think the release date has been officially announced yet but rumors have been that you can get one starting from july.
5) No idea, they just said 'some cosmetic changes'
6) HTML and text files are certainly supported on the iliad. The new readers are just to make life more easier. Some readers allow more things on iliad like opening word files.