I got the "Updates Ready" alert on Thursday, so went ahead with the #2004 Windows featured update. What a nightmare. Couldn't get online, reboots would take forever, 30 mins or more, then I'd get online, but something else would crash and I'd get knocked off again. Sometimes no start menu or no task manager. I ran tests for corrupt files or disk problems and all good. I finally gave up and rolled everything back this morning (you never know if that's going to work). Rolling back, thankfully, was painless and all is well.
One of the known bugs is with some display drivers if you're using a dedicated video card, so update those first before you attempt updating Windows. There are also known bugs with networking and wireless cards. Around 10 bugs that they're admitting to, but I'll bet there are a lot more.
So, my advice, make sure you have a backup and hold off clicking the update now button for a bit until they address some of this stuff.
Resolve then, that on this very ground, with small flags waving and tinny blast on tiny trumpets, we shall meet the enemy, and not only may he be ours, he may be us. --Walt Kelly