Originally Posted by Psykhe
To answer myself, yes, there are definitely upscaling issues with the new resolution.
a closeup comparsion of a "b" from jswindens example (left PW, right KT).
Note the far higher amount of grayscale pixels on the PW. With the KT you have far more "hard" edges, which makes the font appear sharper.
Wow, that does explain a lot.