I'm in the starting block for the One.
I have the glo HD which is perfect for a 6" device, and a H2O which was my preferred reader until the glo HD. Unlike many on this forum, I think the screen and lighting quality significantly better in the glo HD, and my small arthritic hands find the size and weight more comfortable, and of course better in transit.
BUT, I do most of my reading at home (hours a day - mostly a night), and whether on my sofa where it fits on my thigh, or in bed, I never had problem with the H2O, and the One is lighter. Also, a number of my books NEED the even bigger real estate
- unconvertible PDFs (those greying rare books unavailable otherwise)
- most poetry
- books with looooong sentences: Proust in French for instance, and those German books where you need the verb at the end to unterstand the whole
- books with tables and graphs or maps.
So yes, I'll buy, as a completion of the range I need. It is an upgrade in screen quality respective to the H2O. I don't know yet whether I will keep the H2O or not, but the glo HD certainly.
Since I read a minimum of 5 hours in 24, and have problem eyes, I would upgrade for the same real estate if there was a significantly better screen, but that is not my main motivation here.