Like others have said they're great files. I have TERRIBLE nails. They're deeply ridged vertically so break downwards towards the quick along the thinner ridges. They're an utter nightmare and catch on everything.
Mr. AE has perfect nails. Smooth and well-shaped. They look like they've oiled and manicured every day even though he throws everything at them. So annoying!
I also use the LD or PF nail files to do a quick job and then finish with the S-R. They seem to seal the edges off better than the rougher LD/PF files so I can maybe last a day without yet another snag. I don't use them to buff my nails simply because I'm afraid I might go too hard across the prominent ridge and wear the thinner part. I do buff across the top just below the edge. They look weird as just the whites shine but I'm past caring. Anything that helps stop the constant snagging for me has to be good in my book.
My niece does use hers to polish her nails, but hers are normal like Mr. AE's. She tells me it takes very little buffing (more like polishing without pressure) to bring the shine out, unlike her experience with the block types.
I checked several times with her that she's not buffing too hard as I found it hard to believe that a file that is effective enough to leave a pile of extremely fine dust after dealing with my crappy big toenails would be so gentle on her nails, but it is.
What are you looking for in a file, Strato?