Richard Franiec was nice enough to send me a sample of his custom Nikon J1 grip before he left on vacation for Hawaii, and it's everything I've come to expect from one of his grips. As usual, it's custom sculpted to fit the exact curves of the camera body, and he's done a good job of getting hand position right (at least for my hands). Your middle finger drapes down the top part of the curve while the ring finger locks onto the bottom edge--it just feels "right."
Is it an improvement over the generic Flipbac grip I was using? A tiny bit, as the Franiec hand position feels designed while the Flipbac's is, after all, generic (designed to work on multiple cameras). On the flip side, some might prefer the sticky rubber of the Flipbac to the slightly more slippy aluminum alloy of Franiec's, and the Flipbac is a lot cheaper. Both stick quite well to the Nikon J1 body (indeed, I had to do some very careful work to remove the Flipbac I had been using). I'd strongly recommend that you put one of these grips on your J1, it really does help hold the camera, and neither interfere with any control or operation of the camera. Both look pretty good, too, even the black-on-white the Franiec adds to my J1.
Both grips are easy enough to install. Just be careful to clean your camera first with a rubbing alcohol and let it dry before trying to apply the grip. Make sure you can push the grip onto the camera exactly where you want it by practicing a few times before removing the tape covering the adhesive. In the cases of both grips, once they're on, they're on.
Franiec Recommended Flipbac Recommended
Note that Richard has a variant of this grip for Olympus E-PM1 and E-PL3 users, too.