Honestly? I use it for fun, mostly, at the moment. The first thing I really flexed it for was playing Elden Ring and actually understanding what's going on story-wise, because I love FromSoft's narrative style but without taking notes it's impossible to keep it all in your head.

I'm doing the same with Dune right now (actually doing a reading club thing on Discord) and eventually I'll do so for Gene Wolfe's Solar Cycle, probably the most FromSoft-ish books ever written.

I'm also writing an Elder Scrolls supplement for the TTRPG Mythras, using it to store links / info about obscure websites that seem cool, and generally writing down anything I want to keep written down.

I struggle to understand using Obsidian for scheduling / task organization kinda stuff, because I can't make Obsidian yell at me to go do something. I just use the calendar on my phone and alarms for that. I'm not disciplined enough otherwise. I see Obsidian more like a personal wiki builder.