MuseScore is one of those rare open source projects where it’s obvious that a serious amount of thought has been put into the user experience. I only dabble in engraving, but every time I’ve tried to do something more complex the UI has been ready and waiting to help me accomplish it.
Arguably WYSIWYG engraving software only exists to provide a workable user experience (vs editing lilypond or god forbid musicxml notation in a text editor).
Having worked a fair bit on it and as a regular user of it I'm only too aware of areas still in desperate need of a better UI/UX though. Still hope to go back to contributing more regularly at some point, though I didn't especially enjoy having to regularly deal with the foibles of a large complex C++ code base and digging into the internals of Qt to figure out weird UI bugs.
