Many widgets have delay functions (delaying a search by X ms after entering a filter for example).
A function that could realy use this would be the default progress bars.
Using a blocking bar when a Microflow takes a while is very usefull, but if the flow is fast enough, the blocking bar is very distracting (flashing on and off screen).
Some actions however are often fast, but sometimes take time. In those cases it would be great if the blocking bar only shows if the flow takes longer than a certain time. This way the feedback to the user is not hindering, but only there when realy needed.