I use a Canon clear UV filter mainly to protect the lens because I get into dusty situations. I didn't see a whole lot of image degradation, but I'd probably be better w/o it. What are you guys doing?

having had a damaged front element years ago (from accidental encounter with object) i've always had a uv on. yes, people argue they don't serve any 'photographic' purpose nowadays, and they might be right, but ask them that AFTER they've damaged the front element.

i now have a matt box on more or less permanently so don't use the uv, UNLESS i'm shooting without the box.

I used to always use them, but with the very sensible arguments made by others who know a lot more than I do, namely that any piece of glass in front of your lens will degrade the image somewhat, coupled with the deep lens hood on most pro cams (minimizing the chance of any lens damage other than from blowing sand or the like), I've elected to not use them any more.

Sandy/dusty situations, yes, sure.

Use them in dusty conditions. Otherwise you can do without them. Also, be aware that your ND filter control is another place that dust can enter your camera. Attached is an example of using it while hanging out the side of a land rover. You can also see the effect of a lens shade.