No notable differences jump off the screen, though the fix to Spaces is quite nice. Before, if I had two windows from the same app — Say, Firefox — in two different spaces, a click on the Dock icon would take me back to the first one, no matter what space I was in. This now just takes me to the one in the space I’m in, or else to the first one. I like it.
You might still want to back up, but after bravely facing sniper fire, I declare the update ready to go.