I've just recieved a set, and I think they are going to be very usefull. I'm always boosting the chroma on the deck to add color and fleshtones...but it's not as axact as the Warm Cards.
The only downside; don't white balance on one in the shade and have any sun in the background or it will GLOW. Also if you are in a lit area that is higher than 4000 and there are also 3200 lights around, the 3200 will GLOW and looks bad.
One thing I have noticed if you are forced to shoot an outside shot in the shade, with direct sunlight in the background, white balance on the warm cards in the direct light and the shaded light won't have that blue tint. Plus the background will macth the foreground more naturally.