We`ve seen about ~ 10 - 15% max RAM usage increase overall, but this varied between builds. A few previous builds ago we had a bit higher usage, but now (Build 7685) it`s back down again. CPU usage is about the same, maybe up to 10% higher.
We`ve added some some additional signatures to ClamAV and this also increased its RAM usage, but that is another story.
We have sufficient RAM and it would not be a problem if SM used more to do caching or to improve performance - as long as the higher RAM usage is not the cause of memory leaks or other inefficiencies.
I think the biggest impact on performance anyway is the disk I/O. Our data resides on NVMe drives and performance is quite good, especially now after many efficiency improvements.
Our install maybe is not the best showcase as we do not really have that many users (there are many installs with way more than 400 users) but we are quite active and have many different users stressing the Web Interface, Outlook and other clients in various ways.
The most important thing is that issues that we open tickets for are usually fixed in good time, except for those that are the cause of Microsoft products or require Microsoft`s involvement, which are a pain as sometimes these affect higher-ups so there is a lot of pressure.
Right now SM is quite stable and good for us in general. As long as future updates do not introduce any more major issues, it`s fine.