Either the dial or swiping can be used to navigate between screens. You access widgets right of the watchface and notifications left of the watchface. You can use the dial to select an app, a button on the side to take a step back or a different button on the side to return to the homescreen.
S2 runs Samsung's own Tizen operating system. It currently has a lot less apps than Android Wear or Apple's Watch OS and a lot of third-party apps perform badly on the device. It's unclear if developers will start to develop Tizen apps in the near future.
Because the strap mounts for the standard model are unique, it will be difficult to find different straps to use with the watch. The S2 Classic has standard 20mm quick-release pins, but that is not available as a 3G variant.
The interface takes some getting used to as apart from dedicated home and settings buttons, the navigation feels random - sometimes swipes don't work where you'd expect them to work, sometimes cycling doesn't work where you'd expect it to work.