I got a Spotify update a couple of weeks ago, but offline playback wasn’t available at first.
However, when I checked again yesterday, it had appeared (no new app update, so it must have been a server-side change).
It’s very basic, but it works. I downloaded a playlist and did a quick test—it seems fine so far.
One major limitation I’ve noticed is frustrating: you can download a playlist and play it, but you can’t shuffle it. Playback has to be in order. You can pick where to start, but it will continue sequentially.
I like shuffling my music so I never know what’s coming next.
Later, I’m going for a short 7km run and will test leaving my phone at home to see how it affects battery life. I usually don’t listen on this route, but I’ll turn it on with the volume very low