I discovered that recently, it's a very fun way to contribute to OpenStreetMap, and the UI is really well-done, it's totally beginner friendly!
I wish there was a way to do more than labeling though, like add simple roads and footpaths
It's very intuitive and makes you learn just how detailed and specific map data can be. Can't say much about missing features since I don't event know what can be done.
Recommended experience, it's like playing Pokemon Go without the evil part :)
Maybe it's a useless nuance, but I don't think Pokemon Go gamers should feel/evil or even that they should be careful the next time they try to entertain themselves.
Open-source software and data are obviously public goods I support. I was just pointing out that the only "evil" parts here are rent seekers reselling this data and the military... not the people assembling the data (players).