You should always do your homework by searching online before asking you know. :nono:
This has been argued to death before - get filter to "protect" if you feel your lens is worth protecting; don't get it if the sharpness/image quality degradation bothers you. Note that good quality (a.k.a expensive) filters degrades the image quality less than bad, cheap filters.
Also, there is a case (in other forums) where the filter shattered and scratched the lens when the camera was dropped, making it a moot point about having filters "protect" the lens. On the other hand (again in other forums), someone dropped his camera, lens first, into the mud and was glad for the replaceable filter protection. :dunno:
Lastly, there will be some who will advise you to use the lens hood + lens cap for protection, as opposed to filters. Ultimately, it's your call, your choice.