I have an N2A card for both my Nook Tablet and Nook Color and they are awesome. To answer your questions.
Favorite ebook reader- Aldiko
Favorite Wallpaper- Zoomfield
I dont really have a favorite app but my favorite launcher of all time is Tag, I dont use it on the N2A cards but it is still may favorite.
Now on to the other topic that this form has generated. Android is open source and not free there is a huge difference between open source software and free software. Open source software is open and free to everyone so anyone can do with it what they please free software is free to everyone to use how the developer says you can.