The image quality is ok, but not stunning. I haven't seen the official Nintendo cable so I don't know if it's better or worse than that one.
I do have a major gripe, and that is that the audio and video connectors are too close to each other. If your video cables need to connect to your TV and your audio needs to go into your amp, they have to be within about 15 cm of each other, otherwise you'll need extension cables. Lame.
I see the Nintendo cable has the same problem.