70 owner here. When I bought my car, I thought pretty hard about the 85. My experience and a loaner 85 really changed my perspective…
First, I was surprised to discover the 85 was about 10% less energy efficient than the 70, probably because of the extra battery weight. Then I realized that: a) I've only had one occasion when the 85's extra range would have been useful; b) there's a new supercharger that will make sure that one occasion will never happen again; and c) I've never even range charged past 90%.
At this point, I'm not sure I'd get an 85 or 90 even if it were a free upgrade. The superchargers really make the extra range unimportant, and I'm one of those people that really like energy efficiency. And since range charging has been unnecessary, I wouldn't upgrade from 60 to 75, either!