I bought one of these when they were first release (for like $20), and while it worked perfectly fine with a few games, I returned it due to poor performance in Pinball Hall of Fame.
In Pinball, there was a very herky-jerky feel to the left flipper, which is controlled by the nunchuk's Z trigger. Not only was there a slight delay in the flipper movement, but it literally looked like it was skipping some frames of animation. Very strange. Made it impossible to play with effectively in that game. I first exchanged for another one, hoping it was a defective unit, but had the exact same issues with the replacement. If I could have been guaranteed that it would work with every other game but that, I would have kept it, but it worried me that this would be the case with other games down the line, so I got rid of it.
That said, it worked perfectly well with some other games, such as SMG. I've been half tempted to get it again, now that it's so cheap, but haven't really felt the need.
I even bought the Kama Wireless nunchuk (also by Nyko) at one point, hoping that would be better, but it was worse, in some respects.
In Metroid Prime 3, every couple of minutes I'd get a "please connect nunchuk" message that flashed for about a second (usually in the middle of a hectic fight) and then restored. Very annoying, and while it didn't necessarily kill me, it definitely detracted from the immersion.
Edit:
Incidentally, I forgot to mention that did experience the exact same issue with Resident Evil 4. Except, for me, it happened as soon as I started to play. Totally forgot about that until I read xycury's post. I can't recall if it was the cordfree adapter or the Kama that did this, though. And those lights are ridiculously bright. I guess there's always electrical tape.