I voted 'commando' because lately I have been going sans-UV's even though I own both B+W and Leica filters. In the past, with my D/SLR's, I'd often find myself in dusty or otherwise compromising situations so I would always have a filter on my lenses. It became habit to buy a filter with a new lens and keep it on forever. Later, I began using them only when they were really needed.
My 35 Cron IV came with a Leica UV filter and when I recently bought my 50 Cron I got a used B+W UV to go with it. Being very small and light, they ride along with me when I bring a bag and are deployed when the time is right. After having been one of the UV stalwarts, I was curious as to how things might change omitting the two additional transmission surfaces. The Leica filter is definitely machined out of aluminum and compared to the brass B+W, it feels light and flimsy.
There is something to be said about them protecting the coatings over the long-term, especially from overly-aggressive cleaning. Usually a lens will be more valuable if it was (certifiably) protected for its entire life. Of course this can be hard to prove but with some careful examination with a flashlight, one can see if it has ever been touched (or at least if any marks have been left behind). This gave me some peace of mind when I bought my 35 Cron. In the end I guess it just depends on how much of a klutz you are and if you are prone to spilling or otherwise contaminating your lenses. It's a bit of a mash-up really. There will always be the UV advocates, klutzes and collectors alike and likewise, there will always be the no-filter advocates, oftentimes old-skoolers or optics geeks. To each his own!