Nothing, everything runs great although it has the typical Mazda HLA ticking until warmed up, and the top pinched itself.
When I got this car it was rough cosmetically. Mechanically the car was sound. After some minor bodywork, major detailing, and replacement of OEM parts, I have had a ball driving the Miata. Summer cruising top down is a blast, and the car is toasty in the winter. It runs like a swiss watch in all departments and looks like it will for lots more miles. Snowy/icy driving is totally out after some hairy experiences.
I made the original post on the 95 Miata around 2 years ago.
This year the Miata has dedicated winter tires on all 4 corners. Driving on snowy roads is not a big deal anymore with the all-seasons in the garage and the new tech winter traction tires on.
The Miata, (or MX5 as we know it in New Zealand) is quite sensitive to tyre pressure on wet, snowy or slippery roads, it needs a bit less pressure than normal to handle the conditions, but will do so with aplomb so long as the tyres are good and the pressure is right.
That aside, it is always important to drive to the conditions.
Here in the States, if you don't have the right gear, (tire in this case) for the Miata in the snow, plus about 80 lbs of weight over the rear end, you better leave it in the garage when the white stuff appears.