I have two Swiss zigzaggers, one I payed for (and had to glue back the plastic bit on one of the setting screws), and one that came with a 201K23. I like it, it's the only zigzagg attachment I can manage to zigzag along edges with. It doubles as an even feed foot when it's set for straight stitch, better than any of the new even feed attachments available at the moment. I'm keeping mine. If I'm ever left with only one sewing machine it might be my black 201. The plastic cover is almost always gone or broken, it was badly made, but the rest is good quality.
For comparison, I have a small neat zigzagger, simplest custruction ever, and it works reasonably well. I have a larger black zigzagger, with four red knob shaped cams for different stitches. It works and it has option for yet three cam sets, (yellow, blue and white). I just can't make it behave along edges and narrow hems. Less need for fabric stabilisers with the Swiss zigzagger.
These attachments work well, just don't compare it to a good swing arm model, the do satin stitches and overcast stitches much better, but for general utility zigzagging their fine.