Mmmm, I think there was a time this was true, but materials are a lot better now. I have 85000 miles on my 2000 convertible with cloth interior and like it a lot because it still looks like new. I leave the top down 80% of the year in Oklahoma, so it gets a lot of humid +95 degree sun and wind. The cloth doesn't get hot, hasn't faded at all and cleans really well. I even had one of those great big Oklahoma bugs splatter its guts on my back seat, which cleaned up fine with a little help from seat cleaner. Now I admit my interior is tan and black cloth probably would get hot in the Oklahoma sun.
Not that I don't like leather, we have in our other cars and like the feel of it.
As for the new 05 mustang cloth, I sat in one at the dealer other day and it doesn't really feel like cloth. Not at all like my 2000. It felt more plastic to me, so I'm waiting to test drive a vert in the hot sun where I can feel it in the most extream condition.
Oh, we have a saying around here for black leather Verts, "Your girl friend will only ride with the top down once". Black gets really hot and is is painful on the legs. I read somewhere that ignoring the interior color, the inside of black cars get 25 degrees hotter just from the paint alone.
I am also waiting to hear from you guys on how well the leather is wearing. Should hear something by the time the Verts get out.