The only downside to the pre-2017 models is the range on pure battery is something like 60m; the 2017 edition roughly doubled that to 111m on a charge.
So far I have not need the range extender and have run it on electric only the past 2.5 months.
Also, it's exceedingly quick off the line - the fast BMW ever made 0-30 which is mostly when I need that capability. Also fun to see the look of shock on Raptor drivers faces when I zip by them in the blink of an eye.