Actually came to write feedback on this. This build right out the gate is doing incredible. Especially with MAPI. I noticed the moment I opened Outlook and just briefly saw "Updating firstname.lastname@example.org" before it disappeared. Normally, I see that message for 10-15 seconds, Outlook now syncs with MAPI incredibly fast. I've also noticed push actions from an EAS device, like deleting an email, Outlook reflects the change MUCH faster now.
Logging into webmail as an admin also seems much quicker, nearly instant, previously there was a ~20 - 30 second delay after logging in to populate our domain list.
I will be monitoring for Outlook restarting itself, we had that issue with the previous build, which is supposed to now be fixed.
We also previously had an issue with customers deleting a large amount of mail, but the domain size not updating automatically resulting in an admin having to manually refresh the usage, will also be checking to see if this still occurs.
Was on build 7544. We held off the last couple updates due to the translation issues. So far, this update is good.