I have an appointment with Tesla this Tuesday to look for a new MS. I test drove a 75D a few days ago. To be honest, I wasn't really impressed with the range when going a little over the speed limit (which i usually do) on the highway (140~150 km/h). We have family living 220km away from us, and at that speed the 75d will probably not reach the destination without charging somewhere along the way.
Keep in mind I currently drive an ICE with a 75 liter gas tank, that is almost twice the usual contents, so I might have been range spoiled all those years.
My daily commute is much shorter and even a MS 60 would be more than enough, but occasionally I have to make ~220km (~2 hour) trips.
Now, I tend to focus on 'can i get there in one charge', and with a 100d the answer would be yes. However, I have to remind myself that getting there is one, but you have to get back as well. The public chargers here are usually just 3,7kW to 11kW, but even with a 22kW charger I would have to stay at my destination for 5 to 10 hours. If I do not intend to stay there for that long, I will have to supercharge somewhere anyway and then the added kWh's of a 100 instead of 75 might not be so useful after all.
I agreed with the family living 220km away that we will install an 11 kW charger there as well so I can get back and forth in 1 trip by charging at the destination(s), but if that was not possible I would have chosen a 85d because I'd have to SC anyway.
So, in my case the justification is that I can reach family in one trip, charge there, and get back home in one charge as well. If that wouldn't be the case I'd have chosen an 85d. For the other trips the public charging infrastructure (city managed charge spots, not SCs) isn't speedy enough for my situation, and a 85d would have been sufficient to reach a SC along the way.