SamMobile obtained a Samsung Galaxy S4 (somehow) and has a detailed walkthrough of the new user interface.
It's more of an update to TouchWiz on the Galaxy S3, rather than a full redesign. Anyone who's used an S3 will note the similarities, and the new TouchWiz Nature UX 2.0 will be easy to pick up.
The Galaxy S4 gets a big camera upgrade, to 13 megapixels, and the Gallery feature gets a makeover, too, though one that seems to have lost some functionality while adding new options.
"There are no options to change preview styles, to Tizen Gallery style etc, like we can on the Galaxy S III and the Galaxy Note II and we really miss this feature," SamMobile said. "However, we really liked the "Content to display" feature in which we could add or remove the content from displaying in the Gallery, for example: from Facebook, Dropbox etc."
The camera and video camera have been fully integrated, so no need to switch back and forth between the two apps, or hit that little sliding lock when using one or the other. The front and rear-facing camera can also take pictures at the same time, or record dual videos simultaneously.
Perhaps the biggest change for TouchWiz novices is the Easy Mode feature, which removes most of the advanced options, presenting a more streamlined interface. Some reviewers have compared TouchWiz negatively to more intuitive Android skins like HTC's Sense, or all of iOS. This option keeps the underlying functionality (and you can turn it back on anytime) while making it easier to use for people who prefer that their device not ask so many questions.
I got a chance to use the S4 myself at a recent T-Mobile event, and I agree with SamMobile's judgments/ In addition, the hands-free gestures worked smoothly, although AirView, which shows previews of content when you hover your finger over the screen, will need a little tweaking, as it's a bit slow to respond.
The Samsung Galaxy S4 features a 1.6GHz eight-core Exynos 5 Octa processor or a 1.9GHz quad-core Qualcomm Snapdragon 600 processor (depending on country), 2GB of RAM, a 5-inch 1920x1080 Full HD AMOLED display at 441 ppi, a 13-megapixel rear-facing camera with 1080p HD video, a 2-megapixel front facing camera, internal storage between 16 and 64GB, an SD card slot that can accommodate an additional 64GB, a polycarbonate body, Smart Pause and floating touch tech and runs Android 4.2.2 Jelly Bean.
Check back for the latest info on the Galaxy S4 as it becomes available.