My demo car was delivered to my house end of March (Dec 2019 build). The thing with demo cars is that ANY issue you note down during during delivery will be covered exactly like you are taking delivery of stock/custom ordered cars with less mileage. My car was offered to me with 75 miles on the odometer for $2560 off which was too good to pass up IMO plus I got 2k free supercharging miles as an added bonus (it's actually 800 kWh of supercharging according to the history on My Account on Tesla website).
I'm considered essential worker so I still get to drive the car when I need to pop in the office and have done the weekend leisure drive around, have racked up almost 2000 miles in the past 6 weeks.
Also, I looked at it this way - with my car as a demo/showroom car, I'm guessing that this was "handpicked" so that it's virtually flawless as I can't find anything that sticks out as far as panel gaps, fit and finish issue that I've seen people discover during their delivery inspection. It would have been in Tesla's best interest to have their showroom/demo car looking at it's best OR any glaring issues was already addressed before it was even put out for demo or have been fixed before it got delivered to me.