I'd say it depends entirely on the video/channel. For instance, on Brady Haran channels (Periodic Videos, Sixy Symbols, Numberphile, etc) the overlays are very

I'd say it depends entirely on the video/channel. For instance, on Brady Haran channels (Periodic Videos, Sixy Symbols, Numberphile, etc) the overlays are very useful as they link to videos about tangentially related topics, followup videos on the same topic, or even other videos on the same topic featuring a different professor explaining things a different way.