It's ok. The library is growing and improving all the time. Offline playback really needs sorting out though, it just seems to struggle. Google Play Music (RIP) used to handle this aspect perfectly and importantly, automatically. Currently you have to toggle offline mode on / off, and even then sometimes things that (I think) are downloaded won't play... It's just not clear what's going on. There's still a problem with a lot of music not playing through Sonos too.