I'm with you on the expandable storage front. For me it's about time. Why should I waste time sorting out books to go on my ereader when I can just pop my whole collection onto a card and put that in the ereader? And then I have all of my books with me so I can swap between them at will.
Here are comparison tables, look for expandable storage in the Memory column:
http://www.the-ebook-reader.com/eboo...omparison.html
http://www.the-ebook-reader.com/ebook-reader-table.html
I've had both B&N and Inkbook Android-based ereaders. I love the openness of Android but it does definitely have downsides. B&N was a lot more simple and straightforward. I just dropped my Android ereader, and am probably going to choose one of these three:
http://blog.the-ebook-reader.com/201...o-walkthrough/
http://www.the-ebook-reader.com/onyx...afterglow.html
http://www.the-ebook-reader.com/kobo-aura-h2O.html - original version with the card slot
ETA: It's easy to find older used readers for a low cost on eBay. The downside is that they may have scratches, damage or worn batteries. But I've had good luck if I just pay careful attention to the listings and ask the seller questions.