So I test drove the new Miata yesterday to see if I had any interest in getting one over the BRZ I currently have. In brief: Wow, what a pleasant little car, I want one in my driveway.
My reference for this will be the BRZ which I believe is valid since both are more less filling the same market space at the same price, although the BRZ will probably get cross shopped against the AWD/FWD platform "fun" cars more so than the miata will, because fixed roof and back seats.
It's tiny, truly small in every way, there is no escaping how small the car is from first walk up to sitting in it and driving it. It makes the BRZ feel a bit big. The motor has useable torque, in fact the whole car is simple more accessible and useable relative to the BRZ. It's faster, feels stronger and is more enjoyable to simply drive in a normal or even moderately enthusiastic fashion. And that shifter... omg that shifter, just... PERFECT. The 86 has been praised for having a great shifter and but in comparison to whats in the miata the 86 shifter feels like moving a stick through rocky mud. It's most obvious when going 4-->5. The miata's shifter is just perfect. Pedal placement feels slightly better in the BRZ but that's likely my familiarity, basically a wash between the two.
As just about every review has stated, yes there's a lot of body roll and yes, it does take away from some of the absolute handling and confidence in working the chassis, but it in no way makes the car less enjoyable. Mazda actually put real (albeit it tiny, 205 SW) tires with a 280 TW rating on the car. I suspect a BRZ with the same tires would be every bit as quick around a race track and probably would chop a few tenths out of the 0-60 difference as well. While both cars have the same fun missive the Miata provide the sensation of movement and "at the limit" with a setup that allows for alot of body roll and chassis movement. The BRZ engineers did it by putting on a ****ty tire that has no actual grip on a stiff, dialed in suspension. The miata also rides considerable better. Going over railroad tracks and road imperfections that produce alot of feedback and even movement in my BRZ were noted and soaked up beautifully in the Miata. Steering feel is roughly the same between the two.
On the interior front, I didn't dig deeply into the infotainment of the Miata, but just a quick dabble put it down as acceptable. The interior is otherwise what you'd expect in a ~27K sports car, which is to say cheap. Lots of hard plastics. It does look more sophisticated than the 86 but it feels less nice to the touch. Due to the seats I'll give the nod to the 86 on this one though, the 86 seats are considerable better in an interior that's otherwise a tossup. The Miata seats don't have particularly strong side bolstering and no shoulder bolstering.
Which brings me to my conclusion on the car. It's fantastic but oddly dichotomous when compared to the BRZ. On the one had it has a more tractable, usable motor for the DD and enthusiastic drives, has a perfect little shifter, rides nicer and is in general a better car than the BRZ...
When you go from the normal or warm driving to hard driving chasing down the last little bit the BRZ is simply better at it. The suspension is more in tune and sharper, where the Miata feels great when not caning it (and the BRZ feels like dog **** here in comparison) when you rev it out the Miata just feels flat in the last bits of the RPM band, there is no reward for spinning it, whereas the BRZ finally comes into it's own in the last 2K. The Miata feels like a special car, fun car, for the 80% of the time you'll be slogging thru traffic, or taking a fun sprint through some curves. The BRZ feels special when you're trying to relive your race car fantasies, keeping the RPM up as high as you can and putting the car on the edge.
So in short the smaller, less DD'able car is the better DD while the more useful, DD justifiable car is the worse car to DD.

:derp:
Both cars are fan-****ingtastic though, and if you are choosing between the two, lucky you. Neither is the wrong choice. If I had a new Miata I wouldn't trade it to get a BRZ. I have a BRZ and I won't be trading it to get a new Miata. I do however want to buy one for my wife so that I can steal it at every opportunity. To simply drive on a public road in a semi normal fashion, the Miata is the better, more enjoyable car.
C/N: The new miata is fantastic, everyone should has one.