I’m using the latest version, 4.0.3.
With a Sketch file saved by Sketch 57, the assets are exported at a much lower quality by Lunacy than they are in Sketch. Here is an example of the difference in quality:
The Lunacy export is much smaller and has substantial aliasing that is not present in Sketch’s export. Exporting at 2x or 3x in Lunacy seems to scale using the 1x asset, instead of using the full-size asset, resulting in an even lower quality.