Version 3.1 brings a new user interface along with a bunch of other improvements to their free iOS app (App Store link):

Major UI Refresh!
New sidebar menu for quick navigation.
Sliding panels on the iPad for greatly improved navigation and ease of use.
Updated colors and graphics.
Improved sign up experience.
New app icon.
Support for Post Formats.
WordPress.com Reader and Quick Photo added for the iPad.
New Simple post preview feature for the iPad.
All new WordPress.com stats.
New WordPress.com Friend Finder feature helps you find your friends blogging on WordPress.com.
Landscape orientation support throughout the app.
Easy access to your site – view it and access the web dashboard right from the app.
Last but not least - many reliability improvements and performance tweaks.

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