Upload & Sell: On
Jerry -- Here's my take on the subject:
1 - Do you or don't you use filters? Yes, sometimes. For example, a recent trip to Yosemite, I used Hoya Super Pro 1 UV and Nikon NC UV on my 16-35L II and 24-105L IS respectively, all the time I was there. These were my most used lenses. The 16-35 with Hoya became completely coated in spray from several waterfalls -- dripping off the front (I used the 1Ds3 on that lens!), wiped off a few times. I'm happy to have had the filters in place. I didn't install on on the 100-400L IS due to reports I've had of poor optical performance, and I didn't use the lens under intense conditions.
For adverse weather conditions, and all event-type use, I cover the lens with a UV filter.
Also used are CPL, ND, and Grad ND filters on occasion.
Otherwise, usually no filter is used, only a lens hood.
2 - What brands do you recommend? Hoya, starting with their Super HMC types -- reliable and best value for me. Secondarily, B+W.
3 - With regards to a CPL, what brand is the best? Meaning: cost is no object? I find B+W Kaessman multi-coated are best. But I generally shoot with Hoya Super HMC or Pro 1.
4 - Am I nuts for not wanting to use a protective filter? Yes, if you are in the elements. Even after a year or so, there is a strong build up from the atmosphere here in Southern California. Partly this must come from home and office interior "off-gassing" of upholstery and carpeting, etc -- I see the need to clean the filter or front lens element once or twice a year while it's been kept under excellent care. I've also seen minor scratches over time in the front surface of my filters. You do the math! If the filter isn't seriously hindering my IQ, I'll use it until there are noticeable fine scratch marks which could affect IQ to some degree. I don't want that happening to my front lens surface! I tend to keep lenses a very long time.
I suggest a prudent approach -- test to make sure the filter doesn't seriously impact your IQ on a lens by lens basis, and protect those lenses in the greatest danger.
Based on damage that would have been done to lenses if I'd not used a filter in "active environments", I'd estimate I've broken even on the cost over the years. But I've saved a ton of time and hassle by not having to send in lenses for replacement of front elements. In fact, I lost a couple hundred dollars and incurred a lot of hassle trying to sell a Zeiss ZE lens that has a teeny-tiny little scratch from metal lens hood touching it -- following the general advice of forum experts. Ha-ha! Only you can decide what is important to your for you time and money -- everything is repairable or replaceable.
On a weekly basis, I'd say I DON'T use filters about 75% of the time.