Thank you for this new feature!
Here my "2 cents" about few elements:
1)The "auto-width" of each columns.
The minimum column width is too small!
MusicBee (almost all tracks got "...")
vs. iTunes
2) Sub-grouping header
Take a look at "DISC 5 - Hotel California". The header title is left alone at the bottom of the 2nd column. IMO, it should be at the top of the 3rd column. Maybe, adding a rule like this: sub-grouping header at the bottom only if there's at least one track right under the header. Or doing something like iTunes should avoid this issue:
MusicBee
vs. iTunes
3) "Highlight" (with icon) column.
There's some room between the track rating and the track duration to display icons from the Highlight column, like in iTunes (take a look at Disc 2 - Track 1):
I'd really like to be able to display my icons from my highlighting rules, like in iTunes! (well, iTunes doesn't have highlighting rules... I'm just talking about the icon
)