Usefulness of the grip is partly personal preference (where nobody else's opinion matters), partly tied to the quality and features of the grip itself and certainly linked to shooting style.
I love grips for most uses and do at least half my shooting in vertical orientation where the second shutter release is very handy. However, I absolutely hate the grip for the K10 and K20 cameras: clunky, poor ergonomic fit, one of the worst grips to come out of the Pentax factory. Try the MZS film camera grip or the newer K5/K7 grip and you'll see how aweful the grip is for the K10/K20. And this isn't a "my hand vs your hand" issue of fit. I defy anyone to try any of the nicely designed Pentax grips and then still say good things about the K10/K20 "afterthought" grip. The only nice thing typically stated about this grip is the neato tricky storage--yawn--storage doesn't help my shooting in the least. I don't need a garage in my hand to store stuff while I'm shooting!
I only use the K10 grip when shooting with a lens equipped with a tripod collar so I don't actually hold the grip...simply use it for the vertical release. Handheld "walkabout" shooting without the grip is far more preferable to me rather than carrying the brick full of "extra stuff." Also note that I don't use a camera strap and only rarely handhold my camera. When I do, I don't want it to be a photo backpack full of extra batteries, and storage media and spare lenses and tripod pocket and...O.K. I'm exaggerating a little bit here, but really, is the grip supposed to take the place of your Pelican waterproof storage case?
One of my traveling photo buddies loved his K10 grip...and fought with me about my hatred of the worthless brick...he never removed his and slept with it like a girlfriend. Then he got a K7 and it's much improved grip and understands what I've been whining about regarding "the brick" for the K10.
In the end, it doesn't matter what anybody else thinks of your grip. If you like to shoot with it then do so. If you don't then don't.
Last edited by Ron Boggs; 11-30-2010 at 11:09 AM.