In my humble opinion, the new-ish Muse Sounds are wildly variable: they're either very good or very bad. For example, the grand piano sound is exquisite, while the choir sound has so little attack that it's virtually unusable for anything that requires rhythmic clarity.
As an example, here's part of a piece I'm writing for strings. Notice that the balance is way off: the Violin 2 and Cello are completely overpowering the Violin 1 and Viola. Moreover, when we get to the eighth-quarter rhythm that begins in Bar 4, the playback is simply inaccurate: it actually begins each eighth-note late, almost making it swings. This isn't a notation issue; when I change the sounds to MS Basic, the sounds aren't as aesthetically pleasing, but the playback is clear, balanced, and accurate.
To be clear, MuseScore 4 is an outstanding piece of software, and the concept behind Muse Sounds is terrific. I just wish they worked a bit better, and that they resulted in playback that more accurately reflects the score.
Thanks for listening.