The palm grip is an effective alternative way to use a pinch grip handle. A palm grip will develop tremendous finger strength, while a pinch grip will emphasize the thumb strength. For this reason, they are complementary to each other, and you should use both in your training for maximum hand strength.
The palm grip is great for doing reverse curls, using either a loading pin or a cable for resistence. Lateral raise type motions can also be used, or just plain lifting the pin/cable and holding it statically for time. Single reps for maximum weight also works great, just be sure to keep your feet far enough out of the way (lean forward a bit when doing these; you WILL drop the weights on occasion if you are pushing the limits like you should be).