I find that for the heated seats, I always put them on the highest setting first (push the button up towards your dash), then turn it down once it get's heating (which is fairly quick, I have had both faster and slower seats in cars past).
I also found what
Wparsons found, that your leg may sometimes block the vent.
I did also find that putting weight in the back does make a difference (sorry
brzr ) 
My grip and control were greatly increased while going up a steep, snowy/slippery hill. (I did it both ways one right after the other to compare).