UV filters - here starts and endless debate the upshot of which is this::
Some people use UV filters all the time, some occasionally and others never.
One the whole the use of a UV filter for daily shooting is debatable, some people consider the added protection against finger smudges and such to be a greater gain than the slight loss of quality as a result of adding more glass into the lens assembly. Of course the loss of quality is determined greatly by what quality filter you stick on the end which is where we get to one certainly in this debate:
"IF your going to use a UV filter use the best you can afford"
There are a lot of budget line filters on the market (loads in
ebay) and they are simply not worth using - they can cause lens flares and be made of poor quality glass leading to more degradation of image quality.
In general its also accepted that if your shooting in conditions where debris or saltwater might get onto the front of the lens then again, its better to use a filter where you can wipe midshoot and not have to worry about scratches forming on the lens.
Chips in the glass are also something that can be helped against, but these are rarer and any hit which is likely to break the front glass will chip/scratch the glass behind - small chips though it can protect for (thick close shooting to off-road rally driving).
In general some people love them and others never use them - just remember no matter what have your lenshood on!