When playing only. Just navigating it's as fast as it can possibly be, no problems there (tried in excess of 4500 tracks, they all show up immediately, thumbs, title, album, artist, rating etc, depending on the view). The moment the Play or Shuffle buttons are pressed, or if I pick/press on any song from the playlist (which up till that point was very fluid when scrolling) the whole thing 'freezes'.
I tried to see if I wait, if it will start playing at some point, but if the playlist has more than 2500 tracks, something times out or the app is deemed unresponsive and the front end disappears, even if I choose "Wait" when asked to Wait/Close. Up till around 2500 tracks that wait time is 10-15 seconds, eventually the app recovers and starts playing and then all is good.