I've faced the following situation, when there is a pitch zoom gesture, here is the list of events I'm getting:

onZoomStarted
onZoom
...
onZoom
onZoomFinished
onZoom
...
onZoom

Without inertia one may assume the onZoomFinished indicates end of Zoom events on do some app logic related to it here. However, when inertia is on, this is not true any longer, so app logic will break if there was a dependency on running onZoomFinished event after any onZoom events.

Looks like any inertia-caused events should be followed by "inertia-caused" gestureFinished events so that the app may reliably recover after inertia.

This is a major usability issue and it also indicates inconsistency between inertia-on vs. inertia-off touch systems.