Hey, author here :) It varies by the length of the video and some other things, but on a 2019 Intel MBP it's loading up a 35min file in about 5 seconds. After that, it's interactive - you can adjust the silence-finding settings in real time, and seek around and hit Play like any other video editor, and it'll play back while skipping over the silent parts.

The slowest parts are (1) loading up the audio to find silence and (2) if you decide to export an MP4, encoding that. Exporting an XML timeline is near-instantaneous.