In “Design Guidelines for Hybrid 2D/3D User Interfaces on Tablet Devices,” Katri Salo, Leena Arhippainen and Seamus Hickey at the Intel and Nokia Joint Innovation Center present the results of a user experience evaluation made for the user interface of four 3D UI applications.
Among other things the results show that users wish that applications had less 2D overlaid icons and more space for touch gesture interactions. Second, the number of on screen control elements complicates the activity.
Also, avatar control was difficult as there were no tips or clear cues on how to use them. Finallly, they determined users expected to control and interact with the applications by using direct touch gestures in the 3D space. From these results they have derived design guidelines for hybrid 2D/3D user interfaces