Half of it is real leather - half you are in contact with. But i'd agree - the leather is cold in the winter (hence the necessity for heated seats), hot in the summer, it can sag/stretch quite easily in use. You also lose a bit of the personality of the GTI/GTD by losing the Tartan (OK, not to everyones tastes, but the interior of most VWs is a bit on the drab side, the Tartan breaks things up a little) and the cloth on my 15 month old GTD still looks like new.
The colour is purely subjective - love a red GTD, didn't look right on an R (IMO), I'd be going DBP or Carbon Grey if I was getting another GTD, my forthcoming R would've been DBP if Lapiz blue wasn't on the options list for the R.