I had leather on the Bimmer and have them now in the Audi.
I would NOT have paid extra for them in the Audi, but it came with them, so that was that.
On some of the higher-end cars the leather is fairly soft and has nice gathers in it that tend to wear well over time. Others -- absolutely the opposite. They become shiny and worn looking -- sometimes even cracking (just try to find a mid-80s Porsche 911 with the sport seats that haven't needed to be completely re-done in the side bolsters).
They're in fashion right now, so any high end car has to have them. But James is right, they're hot in the summer and cold in the winter and really slippery.
Even on moderately-warm days, or hot days with the A/C on, I will still sweat through my shirt since the leather doesn't breathe at all. James is lucky in that the S2k's seats are perforated -- mine are not. And as he said, heated seats are a must.
For me, I would never pay extra for leather -- unless I had a dog that sheds a lot of fur or a kid that I couldn't wrap in cellophane.
