I received 2 updates for my Galaxy M11 within a span of like a week, and these are some of the changes that I have noticed till now:
The Good:
1. MOST IMPORTANT : Dual messenger issue has been fixed by Samsung.
In the past few months, many users, including me were facing various issues in dual messenger whatsapp, like pdfs not opening etc. It has now been fixed by Samsung. I think they will roll out a suitable update for other devices as well.
2. The versions of apps such as Call, Smart view etc has been upgraded. Below are the recent versions available at present for my device.
Phone version: 12.1.20.14
Call version: 12.1.02.108
One UI Home: 12.1.07.13
Smart View: 8.2.13.13
3. Security patch has been updated to 1st July, 2021
4. Overall the device feels a little bit smoother, and there are no network or performance issues till now.
The Bad:
Heating issue still persists while charging. When fast charging is enabled, temperatures can go as high as 55°C, which is a bit uncomfortable for me.
I think Samsung has rolled out a pretty standard update. But yeah, there is still ample room for changes and improvement. For e.g. Carrier aggregation, support for goodlock modules, screen recording etc.
Let's hope they implement all these features in One UI 4.
Till then, Ciao.
Here. 
