I got an FC on every chapter 4 map (it took 1:59:41), Guardian took like 6-10 attempts (didn't count)
Here are the notes I took:
1. Typo in the 1.6 update message (consistant / inconsistant -> consistent)
2. The accuracy counter (that's what I call the hit score) seems to be stretched out (Pretty sure this was an issue in 1.5 too though)
3. The Ol' Jitterbug isn't even near "Impossible", the note spam at the end is just not fast enough for that. It should be in "Very Hard" or even "Hard" (depending on how hard you think note spam is).
4. Dark Sanctuary should be in "Very Hard"
5. Mysterious Ringing & Ripple should be in "Easy" (probably, the line between Easy and Normal is very blurred, also is "Medium" difficulty a typo?)
6. Airwaves might fit in "Very Hard" (it seemed around The World Revolving's difficulty to me)