The user interface is the most essential part of a product; the linkage between the user and a device. User interactions define product attributes: pleasurable, clumsy, awkward, classy, desirable or cheap? 
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Traditional buttons, knobs and wheels are problematic; design lines are ruined, holes attract dirt, moving parts are the first to get broken and a plasticky switch is equated to low product quality. Both users and designers value pure integrated designs without anything obtrusive. Above all, users desire positive experiences. 
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A product is desirable when its interaction is pleasurable.