The 1 hour was, as stated, 'once downloaded', i.e. after the download.
The first four times after the upgrade, boot time was 8 minutes each time, but by now it's down to 3 minutes, which is still longer than it used to be.
I assume it may go down further.
I also noticed that, again, Microsoft changed the Default Programs for certain file extensions.
The problem with the icons is only partly solved with WinAero: after rebooting, the desktop icons are all over the place again.
Edit to add: Yes, this is the update from the Anniversary Edition to the Creator's Update.