On its own it looks fine, but if you directly compare it to either the waifu2x'd or the "fullrange" flagged versions, you'll see that the colors don't quite match...
Here's an animated PNG demonstrating the considerable difference at the beginning of the Vita UBW OP (
make sure you're using a browser that support APNG)
Personally I vote for the waifu2x'd versions.
I mean, currently the waifu2x'd versions are the only versions that will actually display the correct colors in "ultimate edition".
(I would have to make new, corrected encodes for any non-waifu2x'd versions)
The non-upscaled versions are only 960x544, so aren't most people (at least going forward into the future) going to be viewing said OPs with upscaling anyway via kirikiri's own built-in mediocre upscaling? (especially when factoring in Hi-DPI displays)
Consider that we're already waifu2x upscaling the likes of the H-scenes rather than just letting the VN engine itself upscale them. How is using a waifu2x'd OP that was originally sub-HD any different from that?
I could understand if the alternative was high-quality real-time upscaling (like uyjulian's upcoming GLSL implementation of waifu2x)...but that's not the case here.