I have one of the early P85's - and the list of changes is quite long - and surprisingly, if I ordered a 90D, with roughly the same performance as my P85, the cost of the car would be about the same - and would include 10% more range (larger batter pack, dual motors), power folding mirrors, parking sensors, included console (which I paid to have installed after purchase), traffic aware cruise control, improved windshield washer nozzles, blind spot warning, lane departure warning, speed limit display, autopilot for highway use, self parking, automatic high/low headlights, summons, improved cabin air filtration, LED headlights, next generation seats, ...
Some people liked the original clean look of the front floor tray without a console - while I paid to get the console added, some people liked the non-console look, and that doesn't appear to be available any more.
Since the early cars, Tesla changed the front defroster vent design. The early cars had a matte grill over the vents - which has since been removed - and in certain lighting conditions, it appears the defroster vents are more visible reflected off the windshield (a problem other cars also have).
Another small change - the "D" cars with the front motor lose a little space (the size of a microwave oven) in the "frunk". Since there's so much storage inside the car (including the storage under the rear floor), the loss of this small space isn't significant.
As of today, we're planning to buy a second Model S to replace our ICE - and we have a reservation for a Model 3 which will eventually replace our classic P85, as the "short haul" commuter for my wife - with the new Model S as our "long haul" EV, likely with at least a 100 battery pack (100D should have 20% more range than our P85) and AutoPilot 2 hardware.