They need to be better than the 3DS pads. Those just don't cut it for long gaming sessions (at least for me). In fact, I'd say that I'm still adjusting to even using them.
But the impressions from the circle pads on the uPad have gotten good impressions, so I'm not overly worried. And precision isn't my biggest issue; it's comfort in the movement, which I suppose leads to a lack of precision.