I have used often Genuine Fractals in my previous job when I was the art director of an organization involved in organizing fine art exhibitions and books. At the time it was almost the only available tool of it's kind and I must admit it saved my day more than once where I had to fill pages and I had no high resolution photographs available. But I could never like the way it tends to smooth flat color surfaces in a way that looks innatural to me. In order to eliminate the unavoidable noise that you have when you interpolate from low quality sources, GenFract creates some visible artifacts which I could never like. If the tradeoff to have less noise must be "jpggish" artifact in my images, I prefer the noise. In fact, I even prefer Lanczos to GenFract. To me, Stair Interpolation Pro is the better choice because it keeps so much detail. And that's pretty much the whole point about interpolation, because, if I didn't care about detail, I would simply use the bicubic in Photoshop. Stair Interpolation Pro surely brings in more noise in flat areas than GenFract. But a wise use of Grain Surgery after Stair Interpolation Pro is going to give you better results than GenFract in 90% of the cases, in my opinion. Anyway now that my job is completely different, I almost never use interpolation. The rare times I do, is to actually decrease detail in images. In fact i almost never antialias my Vue renders. I render them at 4 times the final size then resample them down using simple Bicubic Photoshop (or Bicubic sharper if I feel I need more "punch"). I learned this trick in the beginning of my work with 3D and I have to say, I still ahve to find a 3D application whose built-in antialiasing works better that the "render larger-photoshop resample" workflow. The only kind of antialiasing that I still use is -sometimes- Vue's texture antialiasing.