It's good, but it depends on the map having the details in the first place. e.g. near me, the roads are mapped, and a lot of the town centre, but there's a huge amount missing.

Street Complete can't ask about a building if it hasn't been added to OpenStreetMap in the first place.

I use it once in a while when I'm taking a walk, it's made purposely to fill stuff easily on the go.

For more detailed/complex edits, I go with Every Door.

I've used it quite extensivly, big fan. It asks for further details on objects that have already been mapped, which also reveals things that don't exist anymore. It turns mapping into a really fun game with currently 163 different quests. The app also regularly asks you to verify opening hours or confirm the existence of certain objects. That being said, I almost always use it in conjunction with a real map editor, to add new stuff I find or to make more complex edits.

I've used it

I love that I can easily correct and annotate bike lanes

I use it a lot when I'm on the go because it's just very quick and easy. I also contribute to OSM normally using my PC or Laptop.

Seems like a good way to crowd source finer detail

I've used it quite a bit recently. It makes it really easy to submit data in small amounts. I usually have it open while walking my dog and enter in basic things as I go. I've completed about 1500 quests so far with it.