UV can affect certain dyes and pigments. In the last 20 years, most inorganic dyes and pigments have been replaced with organic versions. This eliminated the use of heavy metals like cadmium and chromium, and it is why the modern yellow and blue VWs are not as pretty as the beetles of my youth. I digress - some of these modern coloring agents can degrade fairly quickly in UV, so it depends on what the maker used as to whether or not color will change.
I would guess that UV would affect the finish, both lacquer and varish. UV tends to promote organic chemical reactions, meaning it will push them toward completion and cure. Exactly how this may affect sound, appearance, smell, and feel, (taste???) I am not certain. I would guess that it would promote "oldness" in an instrument.
I am not sure of the effect of UV on wood, perhaps there is a forestry major on the cafe that can enlighten us. It may be that the finish would consume the energy of the UV, absorb it if you will, so that the wood is not affected. Interesting question.
After reading the various posts on this topic, the folks at Gibson are onto something that is very interesting and may have some fascinating implications.
those little wires are like cheese cutters.