I've been running this since its release, and to be honest, apart from the change of version number, I can't see any difference. Performance is the same, battery life is the same, and reliability is the same.
On the "how much of a hurry should I be to install this?" front, according to Apple ", this update has no published CVE entries," which means that unless you're being plagued by some bug or other that you're awaiting a fix on, you could hold off updating for a while (as long as you're up to date on Big Sur 11.5.1, which contained some pretty important security updates).
To update macOS, click on the Apple logo in the top-left corner, go to System Preferences, find Software Update and download and install any available updates.
Having set this up on a system where I was paying attention to the setup, I noticed that on first boot up users are given an option to set up accessibility features, and to set up Apple Pay on their Macs.