First off thanks to mgmueller for the comprehensive list of devices and their inherent usefulness or lack thereof.
I currently have an older Sony PRS-500. Which I love and use daily on my commute and before bed and whenever else I can squeeze in reading time. Now, while I really enjoy my Sony reader it is far from perfect and I have a few questions on some of the other units.
1. I don't keep too many books on my reader at any given time but I usually have between 20-40 mainly due to lack of proper organization. With the Sony it can sort by author, title or collection. I do use collections for Series so I like that feature but I really wish there were more options to search/sort. Genre, author, read/unread/partially read, length, year etc. Do any of the devices offer this type of support for organizing your collection? I guess it would need to be database driven for this type of organizing. I am probably asking way too much here. But even just to know which books I haven't yet read quickly would be nice.
2. I always liked being able to pick a book from a pile and reads the short description on the back/inside jack. Do any of the readers support this? I know calibre pulls this data when entering in the metadata but as far as I can tell my Sony doesn't make use of this unless I am missing a menu item, which is entirely possible.
3. Being able to delete a book from the reader when finished? I know there is a hack for this for the Sony but I remember reading not to use it if you use collections.
Those are really currently my only shortcomings of my Sony and I am likely just being picky here but now that I know I enjoy the ebook reading lifestyle I could see picking up a newer unit as I originally bought the Sony due to it being cheap as it was used and an older model. I didn't want to drop $300+ on 505 at the time only to find out I didn't like it.