I don't use UV filters.
With regards to UV filters, it's a long debated issue. Here are three pro viewpoints on the issue.
1) Matt Granger talked about this today on Facebook.
2) Here's The Camera Store's own Chris Nichols discussing lens hoods.
3) Lastly, here's a video from DigitalRev where they too discuss using a filter vs going without.
What's the final verdict? Don't waste your money on a UV filter. Instead, use a lens hood for protection.