- Obsidian Sync is pretty slow.
- Obsidian Sync doesn't happen in the background, at present. That means, if you just made a bunch of updates in Obsidian, or you haven't opened the Obsidian mobile app in a while, you're in for a wait.
- Obsidian Sync occasionally has sync errors that involve manual interaction.
That said, it's fine and the overall Obsidian experience makes it worth it (well, if you can swing a discounted price).