I use NValt a lot for simple writing. Recently however, there is so much lag that it's becoming unusable. I'm not an expert, so maybe there are wider Mac issues going on, but they don't manifest as often with other programmes. I'm using a 2010 Macbook Pro running el Capitane. I have cleaned up desktop, dock, run in safe mode, reset various things, switched off dropbox, but nothing seems to make a difference.