Not exactly timely, but I bet I'm not the only one who easily forgets about that particular thing. Most of my stuff is set to autoupdate so I tend to forget.
The upgrade downloaded a large number of packages, I think about 160, during which network connectivity continued to function. After downloading, my router PC reset, and that first boot after the upgrade took quite a few minutes. I ended up running the 90 second timer out after which it reset to 20 seconds a number of times. I was just about to start digging for an HDMI cable to see what when I heard the router beep and my internet came back. Perfect upgrade, didn't need to fix anything afterwards.