I love it. I have used it for very long time with and without extensions. I love the overview in particular, pressing meta and having everything presented to you is fantastic. I used it by mostly running maximized windows, then each time I wanted to switch to another program I pressed meta and clicked on the app I wanted. I used workspaces to keep separate groups of programs for each workflow separate too.
If I used extensions it was small things like Appindicators and small cosmetics like blur my shell.
Now, I don't think GNOME scales very well if you use tens of windows at once, you would need to use too many workspaces, which are slow to navigate, and/or have tiny windows in the overview, which are hard to click because their position is unpredictable unlike traditional taskbars, where the programs are always visible and never move on their own.
My workflow never involved too many windows, so I never had problems with it.
Something else I wish would change is that the top bar should go away or actually do something other than show the time. I would say either just take it away entirely and only show it in the overview. Or turn the clock into a notch. Or just make it a half-traditional taskbar, with the clock and options moved to the right and the left side showing as many programs as they fit in thin bars.