I recently bought Zeiss filters for the first time, to pair them with Zeiss Loxia lenses, and the first results are very satisfactory. It is difficult to say for certain that the filters made the difference, unless I had the same photographs taken without them, or with another make of filters, but I just upgraded some other lenses with the same filters too. I was surprised to see their resistance to flare when taking photographs in direct sunlight.
When you buy an expensive lens you want to protect it and at the same time you don't want to affect the view/image seen through the lens. This zeiss uv filter proves that fine quality glass is worth the money! You should definitely stay away from those poor quality filters!!!