"I've been downloading for 2 hours, 3 more hours to go. "
That is a surprise for me too! I have an appalling connection (2mb/s download) but for some reason, this particular update took, for me, an outstanding 1h 40 minutes only.
I had some difficulties with a fresh install (ISO made from ESD), as it could not find my network adapters. A few restarts and an overnight rest seemed to have solved the problem. I was completely cut off from settings, and I am guessing the reason for the problem was it was automatically downloading and installing the update mentioned by Trouble
So far, for the functions I use, I cannot see any outstanding changes from the previous build, but still investigating.
P.S. Agreed, Trouble. When I attempted to access "People", I got a lockout on a couple of other features. I needed to log out and in again. I am also having a problem getting the weather App to default to my location, but I have had this problem on earlier versions, and it seems to take a while, and a couple or so reboots.