Yuck. The Start Menu is a step backwards. I kept all my files handy via the recently used and pinned (by app) lists. They've made that much uglier.
I had horrible performance post install for quite a while - the disk was thrashing. I suspect some indexing or updates were still happening. It finally went back to normal.
It's jacked up the colors I'd set on the personalization scheme - in particular on the lock screen.
Outlook is doing weird things after the update as well. It won't let me click and drag messages to folders. (A work-around for this is to press the Escape key and then you can move the message.) It keeps resetting the view as well.
At this point, I see no reason to actually apply the updates to my other machines. Hopefully some of this will get sorted out in the coming days before they force the update on me.