Smart phone user interface is simpler to that of PC. But it worsens in one aspect of PC user interface.
PC user interface is complex. For example, mouse has right click button which many users (like my wife) don’t care about. keyboard has many function keys which many users don’t care about. PC screen shows many objects in tool-bars/menus which many users don’t know their meanings.
On the other hand, Smart phone (or WEB) offers “see and select” user interface. Users has only to see several objects(icons or texts) and select one of them, and repeat it. Moreover it’s a direct manipulation by finger. This simplicity of user interface, besides mobility, must be the major factor of the boarder adoptions.
By the way, PC user interface heavily relies on hands/fingers to give information to computers, and eyes to get information from computers.
Smart phone has smaller screen. Users must be more focused on the smaller screen. Smart phone is mobile but users must hold it in one hand and operate on it by the other hand. That is, smart phone occupies user’s eyes and both hands more than PC. It worsens PC user interface in a sense.
Voice interaction is going to make eye/hand free, but its use is limited to closed environments.
It industry should offer better user interaction.