Steps to reproduce
Open up the iOS app and start typing
Characters appear on the screen as soon as I press each key.
There is significant lag between pressing the key and the screen responding. At some points when typing I can be typing 2 full words ahead of what is actually displayed on screen. The characters on screen seem to update quickly, then pause for a second and the screen freezes, then moves quickly again, then freezes for a split second again, etc.
Tested this on iPhone 6s and iPad mini 4 mobile app, same thing happened on both.
To eliminate the possibility my device is slow I also tested typing in other apps - they responded just fine. I also tested typing in my Dynalist document but via the web app in Chrome for iphone, this also worked as expected and characters appeared on the screen as quickly as I typed them.
Sometimes pressing into a line to start editing it also has a significant delay between pressing the screen and the action occurring (eg being able to edit the line).