Overcast says its Smart Speed feature has saved me 30 hours (over the last ~5 months), so I expect it to save me 100 hours within a year. It is especially useful for podcasts and language learning material with a lot of pauses, but I have become used to it, and so I now keep it enabled for most audiobooks that I load into Overcast just to get the dynamic playback speed.
Maybe this will be unpopular, but I feel like speeding up podcasts is really disrespectful to the creator. It'd be incredibly rude to tell someone in real life that they're talking too slow, and in my opinion this is the same thing. Podcasts don't need to be so transactional.
It definitely isn't the same thing. I kinda understand why you think that way, but it's pretty much completely illogical (see avoiding ever skim reading anything written by someone, or never fast forwarding any filmed media where a person is speaking).