We continue to have the same speed issues here.
We've even gone so far as to rebuild our database from scratch using one of the basic FM 13 templates thinking that there may be some CSS or other info that didn't convert very well and was slowing down the system but this has not really helped much.
I know that turning off auto-save can make things faster but this would require us to totally redo the way our databases work and the popups asking to save are quite annoying and unprofessional.
Hoping for an official fix from FM soon for this.
I have also seen the "greying" out of the screen. I believe this is when scripts/triggers are being run, calculated fields are being updated, or conditional formatting is being done. Do you have a lot of scripts?
Have you tried making a vanilla db with only a few, non-scripted/triggered fields and seeing if the problem still occurs?
I hope this is something that will improve as the technology evolves.