This demo basically display a textbox (window), but that have a background whose color is chnaged each HBlank with various PPU writes (only the BG color is changed to have the shortest timing possible).
The NTSC version allow for a 26-tile wide window, but the PAL version only allow for 25-tile wide window (the 26th would be flickering due to slower CPU).
Now the NTSC version appears flawlessly in Nestopia and Nintendulator (before it had glitches) I don't know how it does on real hardware.
The PAL version have glitches on the far right, but on the real hardware they are significantly less noticeable than in Nestopia. Also, if I wait one CPU cycle more, the image appears perectly stable on both Nestopia and Nintendulator, but on real hardware is shakes horizontally ocasionally and that only on half of resets (yet it's still innaceptable). So I had to wait one cycle less and make glitches appear on the right (the numbers after the instruction in the source may not be the correct ones, I didn't care to change them, I just go for the trial and error when doing timed code).
EDIT: I'm uploading the files directly to the forum since it is now possible, and I don't have a website anymore.