Back in 2002, Don Norman did an about-turn on function leading usability and claimed “attractive things work better.” This impressive chapter on visual aesthetics, expands on this claim, with examples ranging from da Vinci to the iPhone. (Also keep an eye out for the Harry Potter skins!)
It should come as no surprise that the visual aesthetics of interactive systems, both hardware and software, may affect our evaluation of other system attributes. Hence, the suggestion that “beautiful is usable” that is, beautiful systems are considered by users to be more usable (Tractinsky et al., 2000).
They also give a framework with which to think about visual aesthetics:
For the full entry, see the InteractionDesign.org chapter.