I use a Nikon D70 and use a UV on every lens...this is for protection as far as I am concerned and keeps the main lens clean. If I don't have a lens cloth it is easier to gently wipe the uv filter and be clean again without worry about the main lens. Other than that, I have not noticed any problems with using the uv.

I also got a circular polarizer and find this to be very beneficial in certain situations. My mistake was piling it up on top of the uv, making a stack that had more vigneting than I would like.

I am considering a graduated filter to block highlights from blowing an image but must consider the mount for this. That is likely my next purchase but thinking about it and directons in my photography.

As for any sort of magifier "filter", I have not used but would certainly prefer the lens to do the work without an add-on which might degrade performance. As it is, I need all the performance I can muster! LOL Tom.

Let us know what you get to using and how it works for you, ok?