I bought a new 2019 M3 SR+ in June, and will start by saying that overall I really enjoy the car. It is absolutely a delight to drive. Being my first EV, I can say that I've learned quite a bit. The first, and most asked thing I've learned is about realistic range.
My conclusion: this car has an advertised range of 240 miles, but expect about 75% of that (180 miles). Why? because the 240 mile range is only achievable under unrealistic conditions.
I've now done a good amount of driving around town and on trips of 200 - 400 miles. I've certainly enjoyed monitoring the energy graphs and keeping notes, and can see that there is nothing wrong with my M3 SR+ battery. What I've learned is that driving in an ordinary fashion - that is, keeping up with the flow of traffic, climbing hills with the flow of traffic, being in stop-and-go traffic, and driving interstate highways at the speed of traffic (slightly over speed limit) - will require a significantly higher load than the "rated" load of the car of 247 wh/mile.
Can I get lower wh/mile figures? Sure. If I drive slower than traffic around me, or stay put at 60 mph on an interstate with a 70 mph speed limit. But that's not realistic. I'm not trying to drive like a nut, or show off the acceleration. I'm just trying to drive the car much as everyone else drives their ICE buggys. What I find is that I'm averaging around 280 - 320 wh/mile much of the time, driving the M3 like an ordinary car. And that translates into lower than advertised usable mileage per charge. If I use percentage of charge rather than miles, then I know that 100% = 180 miles, and a typical daily charge of 80% = 144 miles.
Example: last night I drove almost exactly 100 miles from an 80% charge. It was an interstate posted for 70mph, so I set cruise control for 72mph and changed only when I had to. I got home with 15% remaining, which is consistent with a total range of only 154 miles (less than 180!). I'm sure that the high speed and rainy conditions cut into my efficiency, but that was simply part of driving in the real world.
Looking forward to the much better batteries of the future.