[BMarkmann]

The output in their screenshots look nice, but it looks like there are some cases that aren't handled as cleanly as I suspect LilyPond would render them. In the "Praeludium 10" screenshot on their website, look at the first sixteenth note in bar 21, for example. It's rendered really close to the left margin (and obscures the tempo marking); most printed scores would include a tad more padding for readability. Would be interesting to read their layout algorithm and compare it to Lily's (I guess I can!).

[Cardshark]

Wow, that's weird. I downloaded the score in question (https://musescore.com/opengoldberg/scores/719586) and opened it in MuseScore, and found that for some reason that's the way the score's style controls were set. The "Barline to note distance" (under the Style menu in MuseScore, choose "General…", and then click "Measure" on the left) is by default 1.2 times the space between two lines of the staff. But in this score, it's 0.6! I have no idea why—changing that parameter back to the default seems to yield a much better layout.

There's also something else going on with that screenshot, though. The person who took it put page breaks in different places than in the actual score, which is why that tempo marking is overlapping. If you open that same score in MuseScore, the tempo marking is positioned appropriately.