UV/filter use is subjective. Anything you put in front of the lens is going to degrade the image quality to some extent. Each filter has its uses, some effects cannot be recreated in post processing, but each will have a negative effect on ultimate image quality. UV filters are useful outdoors because they cut out the redundant ultraviolet radiation, which cannot be noticed by the human eye, but can be detected by the camera, resulting in a less 'hazy' image. Indoors, at night, or, in certain cases outdoors, they are pretty redundant. As for the protective qualities of filters, many swear by them, slapping a UV/Sky filter on everything and leaving it there. However, as far as impact and breakage go, a filter may do more harm than good. I have had a filter smash through the front element of an expensive L-series white Canon lens in the past, had the filter not been in place, the front element may not have broken. On a top quality lens there should be a degree of dust and water sealing (though this is not always infallible), and it should be kept in mind that if you do have a direct hit that breaks a filter, what you end up with is an abrasive paste of sharp, hard, tiny glass particles in a thick, gloopy, hard to remove, paste of paint. Filters also vary widely in quality, I would avoid the cheap ones, and those on ebay (which may well turn out to be fakes) or suppliers you are not sure of. Some more in-depth info
http://photography-on-the.net/forum/showthread.php?p=9349882#post9349882&postcount=1
A word of caution on cleaning filters, they should be afforded the same respect as the front element of your lens, not just wiped off on your sleeve, unless, of course, you just don't care about the image quality.
Lens hoods, always, almost without exception, not only do they cut out stray light preventing, flaring but they also help protect the end of the lens from accidental damage and deflect indirect hits from paint! Go for the type that fit to the bayonet fitting on the outside of the front of your lens, rather than the type that screw in to the filter thread on the front, if at all possible. Keep them clean as they don't work so well when the anti-reflective inside coating has been covered in old field paint.
Lens (barrel) protection. There are various solutions, if your lens extends under zoom or focusing then you almost definitely want some sort of protection to stop paint getting inside the barrel. Storm Jackets are good, though could be replicated with something like the sleeve or leg of some old waterproofs. Some use Lens Coat or similar neoprene covers, towels, sweat-bands, bandannas etc. I use sports tape on the rubberised parts (stops them getting contaminated with the nitrates from the paint and going white), switches etc, on the body, and a Storm Jacket over the top. Some prefer to run without any, or much at all.
Body protection. I recommend that screens and displays be protected by the self-adhesive film type protectors, the best I found were for phone screens that I then cut to size before fitting to camera bodies. for body protection there are several types available. The silicone skin 'body armour' type, neoprene, proofed nylon and clear plastic, or combinations thereof, all have their plus and minus points. I tend to use Lens Coat clear back body covers and if its really pissing down, I use a second layer of a proofed Wildlife Watching cover over that and the Storm Jacket on the lens.
I haven't found anything really effective in stopping the grained finish of the body getting contaminated by the nitrates in the paint though, or of cleaning up the white mess it eventually leaves, the moral being, if care too much for your equipment (or don't have adequate insurance cover) don't take it on field!
