I have a similar problem. The editor performance has become really poor and does not feel "snappy" anymore. There is a huge lag between typing and seeing text appear in the editor even on a quite powerful laptop. I tried the v.10.9.2 beta and the editor performance became worse loading my CPU heavily even with the spell-checker turned off. I need a note editor with snappy response in order to be productive. Please restore the snappy behaviour that we all know and love from the legacy editions.
Vidar