Living in Washington DC, it gets very hot in the summer and very cold in the winter. I would say the heat is worse than the cold in terms of it being hard to sit down at first!

The first several years that I drove I had a car with leather seats, and since then my car has had cloth. I definitely prefer the leather.

*edit*
Oh, and I agree that they need care, but if you're only planning on having this car for 4 years, I think you'll get away with pretty infrequent care. The car I mentioned that had leather looked great from '96 to '00, and only started cracking a year or two later.