Personally I wouldn't recommend them to the majority of people. What's the point of buying a nice lens to put an unecessary filter over it? There's no optical benefit, more equipment to carry around and the only time I smashed the front elements of a lens (300mm 4L IS) it cost me around the same price to fix as the cost of a UV filter.
The only situation where I use them is where there is excessive sea spray, blowing sand or snow when I compose my frame and whip off the filter to get a couple of exposures off without debris on the lens.