According to Amazon, here are the improvements and feature additions the new firmware (4.1.0) brings:
Improved reading font that is higher contrast and crisper.
Parental Controls now allow you to restrict access to the Experimental Web Browser, Archived Items, and the Kindle Store.
Support for books with complex layouts and formats with Kindle Format 8.
Support for children's books with Kindle Text Pop-Up and comic books with Kindle Panel View (which allows you to read a comic book panel by panel). Books that support these features will be available from the Kindle store over the next few weeks.
Dictionaries grouped into a collection in Home and Archived Items called "Dictionaries" for better organization
Improved table and image viewing (panning and zooming) on supported titles.
You can wait for the update to be delivered automatically to your Kindle over Wi-Fi or manually download the update to your devi... [Read more]