goldwood, I have a black/black in Texas so I guess that makes me an expert on this topic, ahem!
I would say it DOES run a bit hotter, particularly the top of the dash, but 1) I have tinted windows, which mitigate the effects of the sun, 2) I use a windshield cover and 3) the X has a fabulous dual A/C system which cools the interior down quick. I really don't have a problem and don't regret it one bit.....my previous car was black with a saddle interior, incidentally.
To me black is a "cooler" color and does not show wear/tear/dirt as much as a lighter color leather......there have been posts about the X's saddle interior on this point.