I haven't, I've actually been curious about this app though. I wasn't sure how easy it would be to use it while retaining all ownership of my data. I'm not interested in third parties hanging onto that, nor in software subscriptions (their "Sync" offering). I'd be happy to pay for the Catalyst tier if it's something I end up using, I'll check it out and see how much effort it is to integrate with Nextcloud. I use Joplin now, it's OK, hard to complain for the price but not my favorite.

Obsidian is pretty sluggish on my computer, especially when scrolling even short documents. But that's probably possible to improve in the future and no fault of Electron. As a comparison, VS Code is super snappy even on very large documents.