Even on the demo page[0], there's noticeable lag when typing. I have to delete the vast majority of the content for it to feel about as responsive as Google Docs, which still feels far slower than Sublime Text or anything native.
For reference, I'm on a 2012 rMBP with a 2.3 Ghz (turbos up to 3 Ghz when I'm typing) quad core i7.