Delay for playback:
This occurs with an extremely large number of takes in the project. With the current patch, the performance for new projects has been improved again. You have the following options in the current patch to make older 17er projects react faster:
Change play mode to "Recording independent of playback"
Delete superfluous or all takes in the editing project in the project options (shortcut 'I' ->Project status->Clean up
There is also a new SD Cut option "Copy takes when cutting". This is off by default, as SD Cut does not usually work with several takes per object. This means that not so many takes are copied during the S/D cut.