Introduction and Motivation -- Assessing the Quality and Usability of Multimodal Systems -- System Feedback on Mobile Devices -- Experimental Paradigm to Examine the Affective Quality and Functional Connotation of Feedback in Different Contexts -- Affective Quality and Functional Connotation of Auditory Feedback -- Affective Quality and Functional Connotation of Tactile Feedback -- Affective Quality and Functional Connotation of Auditory-Tactile Feedback -- Investigating Different Types of Feedback in a Mobile Interaction Paradigm -- Conclusion.