The new OS introduces a few new features, including a decent imitation of Apple's dynamic island. However, it runs on the Snapdragon 8 Gen 2 SoC, causing the phone to overheat more than before the update. It is suspected that the HyperOS 1.0.1.0 update causes the phone to run at higher CPU and memory frequencies than normal, resulting in increased power consumption and heat generation. Another possibility is that the OS is not utilizing the hardware correctly, but the end result is an overheated phone.
In practical usage, the battery life drops from lasting the entire day to requiring an additional charge during standard daily use.
The result is a significant decrease in battery life and constant overheating. The only potential remedy is to factory reset the phone and restore it from a backup, but this is a time-consuming process with no guarantee of success. It is unclear if Xiaomi is aware of the issue or if a fix is in the works.
Reverting to a previous version of MIUI may be an option, but this also seems like a lot of work.