Just bought a new Vivoactive 3 at my local Best Buy!

I've also noticed the GPS lock takes a very long time. My guess is also because it is new & is finding it's way in the world, so jury is still out. My son & I went to his cross country meet on Saturday and we both tried to saved the location of where we parked, him on my old Fenix 3 that he's using (lucky) and me on the VA3 and the Fenix picked up the location within a second or two and I gave up waiting on the VA3. We eventually just started walking about within about 5 minutes it found satellites.
Then, the next day, I did my first activity with it and it still took a couple minutes - nothing crazy like my old days with the beautiful 205 where I'd just put it in the window 10 min before a run - but longer than I'm used to with the fenix 3. Hopefully it'll get faster.

SUPER glad I cancelled both my preorders from Sept 1st. I ended up walking in Best Buy and getting my watch before others I know that preordered around that same time lol.

RE: manual laps. I've been all over the place trying to pester about that. Pretty clearly, right now, you CANNOT do manual laps while running. They give you the option to enable/disable autolaps - which implies the functionality to create manual laps (otherwise, why?).
DCR talked about it in his comments that his his version of the firmware, a few weeks ago, the option was not there but he thought it'd be added by launch. As of 9/18, it hasn't been added.
For swimming, you mark rest periods by a single press of the button, then end the activity by holding the button down for a second or so. They need to add that in to running as well, which they DEFINITELY can do via a firmware update... however that'll remove the current functionality of a long press (which brings up the shortcut menu).
They simply HAVE to do this. It makes no sense to not have a manual lap option. I get product differentiation but it's impossible to believe garmin thinks "manual lap" is only for their top tier units. This is still a $300 watch.
I can almost guarantee they'll add it eventually - but it's definitely not there yet.

Did a 7 mile run this AM. GPS lock in about 5 seconds. Tried it a couple times with the same results. That is a good thing. HR a little wonky, I attribute that not having the watch one notch tighter. Was spot on for my Sunday run.
As far as data screens- I went with 4. Would be nice if you could have separate views, i.e., screen 1 4 areas and screen 2,3 different areas. Though no big deal. Easy to read on the run. So far, so good. I am impressed. Nick