Well, the trouble with the algos is they are designed for limited color palettes where pixels have high contrasts with each other. If you try running these filters on some N64 3D graphics, the results are.. interesting. Bright, loud games don't look bad, but dark games look even more muddy and even worse the pixels appear to "swim" because you have subpixel movement in triangles. It's also hard to keep 2d HUD/sprite overlays looking clean, they are the hardest hit.
I am playing around with this a bit but haven't seen much promise.
On the other hand I've spent the past few days rewriting the audio resampler. Got things sounding great but I'm trying to take it farther with either Gaussian or cubic spline resampling.