I don't mind leather seats in the winter, I actually find it rather refreshing. It's the red hot seats in the summer that I don't like, although that isn't really an issue with GNE's leather seats as they're not dark enough to cause a problem. Both of our cars however have black leather seats and it's a literal pain in the arse.

Maybe it's just me being a seat snob again, but once you've had leather seats, it's really hard to go back to cloth.
I find the 'slideability' quite important to keeping comfortable as it means you can adjust yourself on the seat more easily, one thing I dislike about GNE's new moquette is that it's actually too grippy to make those subconscious micro adjustments in the seat that give the impression that it's more comfortable.

For me, the perfect balance was the dark blue e-leather they have on the Streetlites and 16 plate StreetDecks, it's grippy enough to stop you sliding, but has enough slip that you can move easily.