It bothers me very much with multi-disc albums. I have a way of placing all the tracks of multi-disc albums in a single file so they will all play in order without interruption or having to manually choose the next disc, if I set "sort" to "album". The track-sorting system ignores my way of doing it and insists on separating the albums, which I do not want. Very annoying. It is also annoying that every time I add something to my library I have to rescan the whole thing. Legacy mode picks it up immediately from the music folder. And very often the advanced mode does not display the album and artist names as they appear in my folder; in fact, frequently they come out as "unknown" album, artist, or both. Also, I have my music files sorted into folders because it is so large. If I want to browse, in advanced mode I have to browse through my whole library at once. Legacy mode (when it is working) allows me to limit my browsing to whichever folder I want.
As you can see, there are a lot of things wrong with this "advanced" mode. In fact, I think it is awful.