I have the new machine running Golden Gate set up in its final location with both Apple Studio Display monitors connected now, so I can say something about Mission Control, which many claim to be broken.
(Mission Control + Spaces is macOS’s implementation of virtual desktops, with trackpad gestures, keyboard shortcuts and mouse buttons allowing a “bird’s eye” view of all your windows and virtual desktops.)
First of all, it was clear even before testing that many complainers weren’t following the instructions (which can be found in the Tips app in a subsection under “Apps”) but simply using whatever mouse actions happened to work in earlier versions. And in the week I was using it with a single monitor, with a single virtual desktop, and never using tiling or any apps in full screen mode, it worked perfectly.
I don’t use tiling, and put an app into full screen mode maybe once a year, so I didn’t test those. They have both been complained about.
My second Studio Display is normally powered down, and I power it up (via an IKEA remote socket) when I want to use it. Sequoia used to have trouble with this, blanking the main display, confusing apps and sometimes screwing up its settings; this problem is gone in Golden Gate. I chose to add the second monitor to the Goden Gate machine by powering it up after booting, and when I did that the menu and wallpaper showed correctly but I couldn’t move the mouse pointer onto this second display. I cleared this by rearranging the monitors in the Displays panel of Settings so the left monitor was on the left and the right one on the right in the panel. Obviously, that ran some initialisation code which should have been called when a second monitor was first detected, but hadn’t been. If I had to guess, whoever tested this at Apple is right-handed like me and had the secondary monitor on the left, so always did this drag at the start of testing! Certainly it’s a bug, but that’s the workaround. Once done once, the second monitor can come and go without problems, and the configuration survives a reboot.
I normally have two or three virtual desktops (“Spaces”) set up with the secondary monitor set to be a separate Space so I can move the Dock there if I want. This is all working as expected.
There is another bug assigning an app to a Space using the context menu of its Dock icon. This just doesn’t work at all in Golden Gate – it starts on the wrong monitor. The menu is also buggy: both the chosen desktop and “None” are selected! Eventually, I got it back to the initial state where “None” is selected and the app always started on the main monitor. The menu is different with only one monitor, and maybe that works. This feature also didn’t work sometimes on Sequoia, so I suppose Golden Gate is a step forward in that it consistently never works. I’ve just decided not to use the feature.
So, there are bugs in Mission Control, but once I worked around those it’s working better for me than it did on Sequoia, with the caveat that I’m treading a “happy path” in the way I use it.