Digital Home Thoughts: Calling All Digital Photographers: What's Your Opinion of UV Lens Filters?

Here's a question for the photographers out there: have you ever done any serious A/B image quality tests with UV filters to see if there's a difference in your images? What's your opinion about whether or not they impact the sharpness/quality of a lens? When I was buying a D300 battery grip at Vistek (more on that later) the salesperson said that as long as I used B+W or Nikon filters, I wouldn't see a drop in image quality, but if I used Hoya or another cheaper brand, I would. I happen to have Hoya UV filters for all my lenses (except the new one of course). Why UV filters? The appeal is protecting the expensive 24-70mm Nikkor lens I just bought from damage, but I don't want to sacrifice any image quality along the way or the money I spent on that lens is somewhat wasted.

So what's the common wisdom, if any, on the impact of using a UV filter on your lens - are are there better brands than others?