I agree with the comments that leather is too hot in the summer and too cold in the winter, and that you slide around in corners. I'd also like to add that depending on the color (mine's black) you can get really neurotic about cleaning it. Actually, though, black leather cleans up a lot easier than any upholstery I've ever had.

On the plus side, I think leather is waaaay more comfortable than upholstery. I've put 37k on my teg in the 1.25 years I've had it, a lot of which was long roadtrips (12-18 hours) and the leather is super comfortable. I always wear long shorts or jeans and t-shirts, so I never feel the leather is hot/cold. Plus, if you have big side bolsters (Teg's are pretty big, Lude's have huge ones) you won't slide too much. And when you get the temp right, ladies love leather