I just recently went through my whole library with Picard and it worked well while the UI was definitely geared for power users. Really happy with the end result.
There was one UX papercut that ended up messing some data on tracks that I had to correct later: fields with multiple values, like "Artists", show the multiple values like "Beats and Styles; Toni W.". But the field in the UI is also editable as a text field, and if you manually write that with the semicolon, it stores one artist with the semicolon included! It took me a while to realise that I can right click to open an editor where multiple values can be entered and edited separately.
There was one UX papercut that ended up messing some data on tracks that I had to correct later: fields with multiple values, like "Artists", show the multiple values like "Beats and Styles; Toni W.". But the field in the UI is also editable as a text field, and if you manually write that with the semicolon, it stores one artist with the semicolon included! It took me a while to realise that I can right click to open an editor where multiple values can be entered and edited separately.