I am kind of answering this thread oddly, but here goes. My Model S is on order now, so I've been exploring some of these things in depth this last week.
1. Charging: Should I plug in often, or run the battery down some? Is it better for a modern battery to be recharged often? Does Tesla explain all this when you purchase the car? I have about 6 miles to drive to work. Is it a good idea to charge every day, or drive the battery down half way before charging, or it doesn't really matter?
Others have addressed this, but Li-ion batteries don't like to sit at full charge. However the Tesla charger in the car can be set to shut off at any level you want. The recommendation is to set it to 90% and only charge to 100% occasionally and to drive the car as soon as it hits 100%.
Li-ion batteries degrade when the charge is allowed to go to low and when it sits at 100%.
2. Insurance: Good insurance companies for better rates? Things to be aware of?
I'm getting insurance quotes now. So far I've only gotten a quote from Amica and it looks pretty good compared to my current insurance, though I will be adding comprehensive and collision I don't have on my current car.
3. Air suspension vs regular suspension: This is a question I have. Is the air suspension that much better? I'm used to a bumpy Jeep suspension so I assume the regular coils will be an improvement than what I am used to.
We don't know what the suspension options will be on the M3, but assuming they will be the same as the M S/X, I went with the air suspension. Some people have said the standard suspension is more reliable and it may be, though I have air shocks on my 1992 car with auto leveling and I'm on the original shocks.
I went with the air shocks because the Model S is pretty low to the ground (the M3 will probably be too) and I don't want to scrape the bottom on steep driveways. My SO has a Subaru Impreza that rides kind of low and she's always scraping the bottom on steep driveways. The driveway at our doctor's office is so bad I have to get out of the car for her to park without scraping too badly and I'm not that heavy.
4. Sound system: I figure that since I will be driving a vehicle with virtually no noise, I will listen to the radio more often. Can guys with the premium upgrade chime in on if it is an impressive improvement over the regular sound options?
Teslas are quieter than most cars, but you still have road noise. If I want a good high fidelity experience, I'm going to listen to my homes stereo with the tower speakers. Yes the high tech sound system will sound nicer, but IMO it isn't necessary in a car.
5. Service: Nearest Tesla station is over an hour away. I won't need to go probably more than once a year? Do you recommend prepaying for a service plan?
I'm thinking about it. They do give you a price break if you pre-pay. Tesla will build more service centers in the next year. Who knows if there will be one near you, but I'm in the same boat as you with the nearest SC an hour away.
How often you go to the SC depends on whether your car has problems or not. The early Model 3s will have some teething problems. All new cars have them. It will probably be better than the Model S or X, but they will happen.
6. Warranty: I'm buying this Tesla expecting a premium car. What can I expect for warranty? I heard Tesla is very good with customer service, but I hear this from guys who have multiple Tesla vehicles. Of course they will get top notch service. Can I expect this with an M3?
Currently it's a 4 year warranty. I don't know how that will change with the M3, but I expect it will be similar. Tesla will probably be stressed to offer the same level of customer service for the M3, but I expect it will still be better than average.
7. Tesla App: I have a Windows 10 smartphone. Not interested in switching to iOS or Android at this time. I don't expect an app to be made for Windows. Will I be missing some awesome features by not having an app?
Windows is a pretty uncommon OS for cell phones. There are a lot of apps for Android and iOS. I did a search in Apple's store the other day and came up with pages and pages of third party apps. You can do a search and see if there are any Windows apps for Teslas.
In three years Microsoft may have abandoned the phone market. Interestingly I was involved in development on Microsoft's first ventures into the phone market and they abandoned that after a year.
8. Charging Cables: I have a 110 outlet outside my office at work. Anything wrong with charging this way with a regular extension cord? Remember, I only have a short drive to work. At home I have a 220 plug. Is it necessary to purchase a Tesla wall charger, or can I just plug into that?
A 110V outlet will charge very slow. Tesla provides a set of common connectors and cables, but the higher power connection you can get the faster the car will charge.
9. Cold weather package: What is this exactly? Is it necessary for PA winters? I sometimes scrape ice off the INSIDE of my Wrangler windshield, so I'm used to the cold weather with a softop vehicle.
I suggest looking at the videos on YouTube by Bjorn Nyland. He's one of the most prolific video bloggers about Tesla. He had a video about a year back in which he went over all the features that were available when he bought his car and whether he thought they were worthwhile. He got the winter package because he was in Norway, but after a couple of winters he didn't think it was necessary, though if you have back seat passengers a lot, it might be useful. The front seats are heated on all Teslas, but the winter package gives back seat heaters too.
10. Vehicle SIM Card: Would the M3 have a SIM card in it so it is always connected? Who pays for this data? Is it built into the price of the car?
Thanks for any input you may have as I launch into this adventure.
Tesla uses AT&T wireless for their connection. I am not 100% sure it's always free, but I know it's included initially. They do need a way to download updates, so it may always be included.