A friend of mine who has a relative that works at Tesla took delivery of his 3 last week (VIN 800s).
Build Quality:
It's nearly perfect!! The panel alignments are perfect, everything is sturdy and clean, the seals are also pretty good...but still slightly bent in the top corners of windows, not really a big deal. Much better than 57xx Model X...and this car is in the 800s!!!
The seats don't have any wrinkles, and they aren't any rattles!
Space
The car has a lot of space! The trunk is huge, rear legroom and headroom is not as much as the 6-seater X but still really good. The center counsel is awesome!!
The Screen
Coming from the X, it will still take some getting use to. The U.I doesn't seem entirely finished as certain tasks are still not-intuitive but it is still responsive. I still prefer the X/S screen layout but this is still pretty good. Also, it seems that they need to fix the auto-brighness.
Autopilot
He was told not to turn it on till the car reaches 200 miles for calibration.
Mobile App
It wasn't really working properly on his Android device...so he had to use the key card. Kept on getting connection errors and phone key didn't work.
The Drive
Handling is pretty good, steering is nice...it is almost as good as my X.
Delivery Experience
Tesla made him sign an NDA so he isn't letting me post any pics or videos...I begged him! He was told not to let any media or 3rd party gain access to the car. He was told not to take the 3 into any shop for tinting/wash or something like that and not to valet the car.
Also, he said the delivery process was smooth but the reps didn't have any answers to the questions he was asking...probably since the car was so new.
I am not sure why Tesla is so worried regarding this...the car is nearly perfect and a lot of people will like it. The early X's were a lot worse...Tesla has nothing to worry about.
I am nearly asleep...ate to much turkey so apologies if something I wrote earlier doesn't make any sense.