I am excited about all the sorting options.
The problem with all the readers apart from the sony is getting quickly from A to z if you have a lot of books after the sorting
On the sony readers from the 505 onwards if you are say in the author sort field you have an alphabetical list down the right hand side so you can immediately jump to the letter P for example
I miss this on other readers.
An alternative could be to widen the little black rectangle that moves down the right hand side if the window as one scrolls down to give an ability to drag the list down
I do not know if this is easy to do or in any way on your roadmap.
Another wish item would be a collections concept where the books in the library can be separated completely into different groups (this is already an ibooks concept buy i don't think they have patented it yet!)
Finally on the dreaming wishlist front an ability to scroll through large cover page pics just like browsing in a bookstore (with or without basic meta data) for the books in the sorted list.