@John Lancaster,
Ok, this seems to be view-port performance then.
We’re well aware this is a weakness in Blender at the moment.
There are some plans to really ramp up effort here and invest time to see improvements get into master,
they will be announced in more detail soon.
I was curious if this was viewport performance (GPU) or edit-mode performance (CPU), they are fairly separate, both can use some work but mesh optimizations can be done any time and don’t depend on larger view-port projects.