After 5 hours of using MC30.0.18 the only "Unacceptable Behaviour" I've encountered involved the Tag Window.
If I'm in Playing Now with an Active TrackInfo Plugin and the Tag Window is open when I change a view the TrackInfo Plugin remains Visible, to get to see all of the selected view I have to switch to telling MC to display CoverArt.
Plus, there is something I spotted while Bob was on holiday and may have always been around, MC on the Mac is not drawing the vertical dividers/gridlines in any view.