I live in Mississippi, where the coldest I have ever seen is about 20 F in the winter. The seats in my 95 LS are indeed cold and hard in the winter. But they warm up as the heater heats up the interior. In our 100+ degree summers, they are also hot, but not too bad since the A/C works great.
The leather seats in MX-6s are very comfortable and look sweet, and maintained, remain soft if you take care of them. I'd say it's worth the inconveniences in extreme weather.
Tyson
95 LS (For sale)