Summing up all of the questions in this thread into a concise list:
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Exterior:
* Fit and finish on the bodywork?
* How do the aero wheels look in person?
* Monroney window sticker showing range / efficiency ?
Touchscreen / controls:
* How responsive is the touchscreen vs. S/X?
* How does the screen do with glare? With different lighting?
* Is there a browser on the 15" touchscreen? (answer should be "yes")
* How easy is it to use the screen versus traditional dashboards?
* What do the release notes show for the firmware?
* Is the steering wheel heated?
* How do you adjust the TACC set speed? (Touch screen? Steering wheel scroll buttons?)
* What does the range show when charged to 100%. (Yeah, I know slim chance of finding that out unless they charge it in advance of your arrival.)
* Ambient lighting settings?
* Are there trip meters / efficiency graphs? If so, how many and what details do they show?
* What does the touchscreen look like while driving with Nav active? (Where are the turn-by-turn directions displayed?)
* Try the voice commands. How do you activate it? What happens if you say "show me how to get to the nearest supercharger?" or just "nearest supercharger" or "find charging". Or if you're bored, "will I ever find true love?"
* Blind spot monitoring indicator location. On the center main screen display, or is there an indicator in the side mirrors?
* Can a M3 connect to a wifi hotspot while driving? Any restrictions on it?
* Glove box: Can you open it without turning on the car?
* Power meter display: Is there a display to show instantaneous kW power draw?
Interior:
* How well do the vents work?
* Seating materials - comfort and durability?
* What are the differences between standard and premium seating? Is premium leather? (answer expected to be: No)
* What are other materials covered in?
* What colour are the materials, and are there any choices?
* How many hot dogs (in the bun) fit inside the center console?
* How hot does the car get from the glass roof?
* How good does the sound system sound compared to your X?
* Are the phone docking stations really inductive charging pads, or do you have to hookup a cable?
* Are the inside handle to open the rear doors electronic buttons? Is there any easily accessible emergency/manual handle like there is in the front?
* Does the drivers side sun visor have a lighted mirror? (answer should be "yes")
* Are there floor mats?
* How much noise does the HVAC system make in the car when the fan is set fairly high?
Access to the car:
* What's the door unlocking experience like?
* What's the range like (for both phone and card unlocking)?
* Does the card have to be in the center console slot when it's being used to drive?
* Does it match up driver profile with the bluetooth phone?
* Is it localized enough to know which phone is sitting in the driver's seat rather than the other seats?
Driving experience:
* Road noise?
* Motor noise?
* Balloon squeal under heavy acceleration?
* How is the visibility for the driver?
* How firm is the ride?
* Is it prone to bottoming out on a steep ramp / driveway?
Warranty:
* What's the warranty on the drive unit?
Charging:
* Is the charge port sealed well (e.g. safe against high pressure spray from a car wash, dust, etc)?
* What CCS charging options will there be for Europe?
* What's the max charge rate for a Model 3 on a CHAdeMO adapter?
* How much external noise does the car make when Supercharging at a low SOC?
Trunk:
* Dimensions? (bring a tape measurer!). Opening said to be 18.5"x42"?
* Does the rear seat lay completely flat (like sleep on it flat)? (should be "yes", and 6'9" long)
* How does opening the trunk / frunk work without a fob? (Can you kick under the car to open it? Is there an external button to push? Do you have to open the app on your phone?)
* Is there a glow in the dark emergency open handle in the trunk?
* Nets/hooks/tie-downs?
Questions - some likely to be answered, most not:
* What works without a net connection and what does?
* What's the planned billing schedule for a net connection? Can you pay-as-you-go per GB without a monthly fee?
* How do you get to the jumper posts if the 12v battery is dead?
* When do we get the official EPA ranges?
* When can we see additional interior colors besides black and white? What colors are contemplated? Cream?
* What is the price for Supercharging? Can lifetime be bought?
* How will service be handled? Do we bring cars in or will they pick up? Are loaners provided?
* Maybe you could take pictures of the entire paper manual that should have come in the glove box.
* Will a roof rack be available and if so with which roof options?
* Can the windows stay clear of frost in extreme cold (say, -40°C)?
* Is it possible to put a hitch on, and/or are there any mentions of towing capabilities?
* Will there be option for Sirius/XM radio with Premium package?
* Does ESC wake torque sleep?
* Is it possible to disable torque sleep?
* Pricing on AWD / dual motor?
* Does AWD / dual motor come with a towing hitch?
* What exactly does non-PUP look like?
* Is M3 designed to be compatible with Supercharger V3? If not, will it be possible to upgrade later?
* Does Tesla have plans for making battery upgrades/replacement available to consumers down the line (fully aware of how expensive it would be), for people whose car has a problem out of warranty or just simply want the latest battery tech without having to replace their entire car?
* Does Tesla ever plan to disclose "hidden parameters", such as any locks on performance or charge rate applied to a specific vehicle?
* What are the actual battery pack sizes, both nominal and usable capacity?
* Does Tesla have any plans for Iceland? Musk mentioned 18000 superchargers by the end of next year - when do we find out where they'll be?
* If someone buys a vehicle in Europe but there's no Tesla store or service centre in the country, how does delivery work - do they come to pick it up? Will they end up getting hit twice by taxes / fees?
* What are general European pricing figures expected to be? Similar to the price difference ratio on the S and X?
* How soon after the AWD version is available will the performance and then ludicrous version become available?
* Will the performance model get any additional extras beyond more speed (sport/air suspension, carbon fiber trim vs wood, turbine wheels)?
* Are there any provisions for a roof rack on the glass roof, or does that require the yet unannounced panoramic roof? (check fofr attachment points under little doors on the roof?)
* What about this alleged inward-facing camera that will be looking at the driver? Will Tesla require that it be on? Will Tesla get weird if you cover it with tape?
* Moonroof / retractable panoramic roof: Will it ever be offered? If so, when?
* Turning/cornering lights: Will they ever be offered?