UV filter can degrade image quality and increase possibility of flares and ghosting. So if you are going to use one, just some simple rule of thumbs to keep the flares and ghosting down. Do not shoot directly at strong light sources. Use a lens hood if you can. And get a good multicoated with.
Super Frequent Flyer, no joke. Ex Patriot and loving it.
Canon Eos 60D, T1i/500D, Eos1, Eos 630, Olympus EPL-1, and a part time Pentax K-X shooter.