I've driven both the i3 and i8, apart from the CFRP they don't compare in the slightest.
As far as driving the i3, it's pretty good. BMW still has quite the knack for making a decent driving car, but it's hard to tell with the tires what they are. The steering wheel tells you pretty well what it's doing, which is good, it is far less distant over the i. I've had no issue with the directness of the steering wheel, I prefer it over the i. There are quite a few corners I make with the i where I need to turn the wheel further then I wanted to just make the turn. My i is pretty restless around dead center, the i3 was a bit easier in this respect.
The cabin of the i3 is nice, but golly is it expensive, and pretty much everything on it was an option. The sunroof, the heat pump, leather seats, navigation, cruise control, ehn, not so impressed. The rear seats, I didn't attempt to get in, I was looking at the car months before I bought the i. But it did get me to consider electric cars.
The price, this demo car was over 45k euro, that is an enormous amount. It's not funny.
The boot was the biggest dissapointment, because of the rex the floor is pretty high, which made it feel very small, especially compared to the rear of the Peugeot 206 SW I was driving before, hah. If the BEV model had the charger next to the inverter, like the i, they could have lowered the floor a few inches and made the boot much bigger or even add another box for the cable. Or maybe even a spare. Although to be fair, they should just loose the frunk and make the spare tire there. Cables can go in the back.
I have a 5 month old kid, with that in hindsight I'd never even consider the i3 anymore, the clumsy rear door access is just too much. In that regard I've been really surprised by the i, I can fit the ISOFIX and maxi cosi and still take the stroller and bags of stuff I need just to get out with 1 baby.
So even if it came onto the 2nd hand market in a couple of years it would still have had the same range (i3 without rex) as the i, which is completely bonkers if you just stand still and think about that for a minute. Why would I choose this car over something like a Kia Soul which goes 30-40% further and comes with a heat pump and fast charging standard?!
Why is the heat pump an option (PTC heater standard), why is the navigation an option (hello 2016), why is cruise control an option for a electric car (my i has one). Too much that just doesn't add up.
So I was like, maybe they'll offer more models with different battery sizes. Nope. Maybe they'll have a upgrade program for the battery, the answer on that is a "maybe".
It's not a bad car, but considering the state of my life currently, it doesn't fit.