personally, while UV lights look cool, they do have some undesirable side effects. UV light degrades plastic over time and is a form of radiation (all light is.) Prolonged exposure to certain wavelengths of UV have been known to cause cancer. This is why tanning booths are carcinogenic.
For most people, short exposures are ok as the body tends to heal itself. But if you have a source that is on all the time, I'm sure it can't be healthy.