Boosts sharpness and clears up details at higher resolutions. Also enhances direct generation at higher resolutions. The sample images were all directly generated at that resolution.
Can also be used to clear up the image in the 'Hirez-fix' step.

Limitations:
The sharpness bias might not be suitable for all styles, try reducing the step count.
There is a bit of saturation and colour bias, so you might have to post-process.