some people do not believe in having a UV filter and some do...
so, it is best to give one's reason why one do not believe in having a UV filter as a protection.

i personally believe that having a good UV filter as a protection is ok... all my lenses are protected by pro one digital UV. its better to scratch (by accident) a rm 130 filter than scratching (by accident) the front element of an L lens... right?

entrapnet...
kenko pro one digital is good... probably one of the best out there currently in terms of coating and reducing flares. B+W is good... but it's hard to find. others to consider will be Heliopan, Nikon, Leica...

the image wkkay posted, it is the one on the left which is a better filter. you can see thru more because the reflection has been reduced by the coating of the filter.