First, can I just say how great it is to now have timestretching and pitch shifting of audio in Cantabile (build 3214) ? Great work, and I’m aware of how fiddly it is to get right! I particularly enjoyed binding my expression pedal to a media player speed control, and accelerating/decelerating through some music 
However, I’ve found one problem so far. If you have left/right markers set to define a play range, it works fine if the audio is playing at 100%, but any other speed and the play range you get doesn’t match the one shown on the timeline - the markers remain in the same place in the waveform (as you’d expect), but when you hit play, you get a completely different range. This happens with both the speed control on the media player as well as the speed control in media file properties.
And on the subject of the timeline, I find the “x” hotkey to centre the waveform on the selected region really useful. However, as soon as you play from the start of the range, it jumps so it’s no longer centred, and then scrolls at the end of the range. I can see this is a feature to keep the playhead more central and noticable; however in the case when you’ve zoomed to the play range it would be nice if this behaviour was overridden. Perhaps the logic should be that if the whole play range can fit within the screen width at the current zoom level, playback shouldn’t cause any scrolling while playing back within the play range. Or something like that.
One further thing - on my Cantabile, “Clear Markers” in the timeline menu appears to be greyed-out, even though I have markers set that could be cleared. So there appears to be no way to clear the markers.
Neil