tl;dr: I still really like it and use it on Mac and iPad exclusively.
My views of it are slightly nuanced depending on the context in which I’m using it. Here’s how I’d define those contexts:
iPad - by itself
iPad - connected to external display.
macOS - Single Display
macOS - Multiple Display
On the iPad with and without an external display, I’ve found Stage Manager to be a true productivity enhancer. I thought that I would use my iPad alternatively in Stage Manager and traditional iPad multitasking with Split View and Slide Over. But I’ve never gone back to the old way. I find it very efficient and enjoyable to use.
With iPad on an external display, I find that a really amazing experience. I’ve run a test for several weeks to see what I could do with just an iPad. For the test, I’ve used my iPad connected to a 27" display through a Thunderbolt 4 hub. The iPad is on a MagFit stand. And, no surprise, I’m using an external keyboard and trackpad. I have some other things connected to the hub, too.
I’m going to write a longer post on that, but the short answer is that it has worked so well that I’ve actually forgotten at times that I’m NOT working on my MacBook. Stage Manager on the external display works phenomenally well. Yes, there are limitations about where windows can be placed. Those limitations have not created any obstacles or otherwise negatively affected how I wok on the external display.
My experience using Stage Manager on Mac [single display] has also been favorable. Same thing with the iPad, in that I have not disabled it since getting comfortable with it. I used to use Spaces and multiple desktops. Stage Manager, to my mind, is basically a variation on that theme of multiple desktops. I have found with Stage Manager active I do not need to use Spaces and I do not need more than one desktop. Stage Manager seems somewhat more efficient to me. The apps that I’m swapping among seem closer to my fingertips, if you will.
Stage Manager on a Mac with multiple displays also works fine but it has some quirks. There are two separate stage (or more if you have more than two displays). That can create some weird interface management issues. Getting a window from a space on one display into a space on the other display is not always straight forward. (I’ve sent Apple feedback on that.)
There were some weird things that I was experiencing early on. E.g., if a dialog box opened, it opened in a completely different space, which resulted in a lot of stage swapping. That is not altogether gone, but seems to have gotten better. When I run an AppleScript, the screen will swap out the stage, run, and then return me to the stage that I was on.