Well it took me under 1 hour give or take a few minutes using home wifi. Some of the directions I thought could have been better and wasted my time putting my watch on the charger when it needed to initially be on my hand. Appreciated the download progress bar but nothing to indicate anything was really happening with verify and install. The download for me was 15-17 minutes I think it said. Think the verify took 10 minutes or so but for me the install was in the area of 30 minutes or so. Like I said no indication it was even doing the install except for the text saying so. I guess I would say be patient.
I also think I could have cut down on my time by putting my watch charger, which was on a stand in the bathroom while doing the update in the adjoining bedroom, next to my phone. If you are reading the thread before downloading I'd say bring them all close together. You do need to have your watch charged to 50% at least to do the Install so take care of that first before the download. Once you start your install the Watch App software will say Do Not Restart Apple Watch or remove it from its charger.
When the install finished my Watch App/General/Software Update screen changed and said "watchOS 1.0.1 / Your software is up to date". Huh??? However I was able to check the Watch App About info to see that it was now listed as Version 2.0. That was confusing. At first I wasn't sure it actually installed the update since it had taken so long and didn't know if it crashed and just put up that screen.
My watch did require a passcode. At some point it put up the Apple logo with the circular ticks as it showed progress finalizing I guess. Then it went black and just put up the white apple logo. And then it completed and I'm off to explore my "new" watch. First checked settings in the Watch App on my phone. Some new ones to check off. I did add the 70 second watch face glance. It's not something that works when you just pick up your arm, you need to tap on the screen to wake it and get the 70 second screen.
Here's a few photos I grabbed as I was going through my install. Hopefully you all see the final apple logo and are good to go.

Then Verified then...
Huh? This screen gave me pause after I had been Installing for last half hour. It updated though. Just confusing screen.

Time to have fun!
BTW I heard about the release being out when I saw the News Alert on CNBC saying the Release was public now. I thought that was funny that a news channel was making that an Alert

(Just think of the significance of that -- the power of Apple and the public I guess -- funny since the news channels have been saying the watch is a disappointment and flop too!) and when I went to General/Software Update it was still showing being current at 1.0.1. I went out of the settings area and went back a few minutes later and the update to 2.0 was then showing.