I'll start with saying that I don't expect much from e-readers. I want a good reading experience, variable text sizes, and some illumination.
Things I've enjoyed and noticed so far:
I like the uneven back, even in my handmade cover, it's easy to hold.
I like the larger screen. Just slightly bigger than my Sony, at the slightly larger than average font sizes (say 14pt), there is still plenty of text on the page.
It's not any heavier than the Sony in my hand
I like the ability to change fonts and margins, didn't think I'd use it at all, until it was one of the first few things I did.
I like that it shows me the covers of the books in the list as well as the titles.
I love the light. 18% - 20% is just perfect for reading in dim conditions. Light seems pretty even.
I like that the sleep screen is the cover of the book I'm reading.
Page numbers on the bottom are nice. (133 out of 257)
I'm not sure what the chapter progress is that everyone seems to be fussing about. Mostly I don't notice chapters when I'm reading an actual book, so that may be why.
I've had a chance to read for a few hours, and finished my book. First thing I noticed, was that swiping on that last page took me back to the home screen, and quite quickly too. That was pretty neat.
I used the desktop to set it up. Since it's not working with Calibre yet, I had a teeny 64mb SD card that I loaded a few books on. The reader found them very quickly.
Tell me what you want to know, I'll quite happily answer any questions that I can.