I got invited to the Instacast 4 beta back in mid-August. I was thrilled to see what changes were made for iOS 7. It's built from the ground up to mimic the iOS 7 styling. It's very minimal, but I like it. The various aspects of the settings section have also been redone to be simple, but still allow power users to have more control over what happens with played episodes, etc. As with version 3, Instacast cloud sync and push notifications are built in.
If you were a fan of version 3, you'll love version 4. Instacast 4 is being released as a free update on 9/18.