I just decided to move forward with a MX 90D (midnight silver, ultra white) to lock in free supercharging and the EAP and fully autonomous hardware. Rationale for me was that the free supercharging is not something I will ever have the chance to "upgrade" to again, but if I wait a month for the next, unknown improvement, I miss out on the charging and then will still want to buy the next best thing a few months later. Harder decision for me was whether to buy or lease - I decided to buy (for now, maybe I can still change), but am nervous about it. I had leased my previous '15 MS 90D, and happy with that decision (it was a test drive model and I got a screaming deal, so it was a no-brainer given the depreciation with technology).
The free supercharging feels different to me, and there will only be a handful of cars with the combination of free supercharging and the fully autonomous hardware. Even thought I don't know exact value of free supercharging yet, seems to me that will make my car stand out and be preferable for buyers on resale, as well as if I decide to keep long term (also a point of stress because I'm worried about MX being over-engineered, but ultimately decided to go with the SUV because I prefer the form factor and plan on getting a Model 3 when they come out - felt like that was a better stable of electric cars than a MS and an Model 3).
Really excited about the car - just hope I'm right and don't get crushed on depreciation.