I principally use Obsidian because it was easy to build out a custom plug-in to easily push a markdown note and its corresponding media to my statically generated website.

While I do wish it was open source, since it doesn't use a proprietary format or alter the folder structure where I keep my notes it's pretty trivial to switch to a different notetaking tool in the future.

Pros

- doesn't mess with your notes or migrate it into a database (looking at you Joplin)

- extensible via JS plug-ins

Cons

- I'm not enamored with the mobile experience