These days, I do almost all my sewing, quilting and dressmaking, on my Bernina. When I first got my 707 Bernina Minimatic it didn't come with a patchwork/quarter inch foot and it was one of the first things that I bought. Bernina parts are expensive, especially in comparison to Janome and I felt like I couldn't really justify £30+ (around $46 USD as current rates) for a genuine Bernina patchwork foot so I bought a generic Bernina style quarter inch foot for half the price. It's the one on the left below, the genuine version is on the right:
As I had nothing else to compare to, it seemed perfectly OK, but I did notice it dragged a little, especially on a single layer of fabric. Check the picture on the far right below- you can see why. The generic foot is scuffed and the base material is coming through. I have been on the look out for a second hand patchwork foot and recently on eBay, my luck came in and I bought a vintage 37 foot- see right above and left on the pics below.
The difference is surprised me. It feels different when stitching and I really notice it at the start and end of quarter inch seams; the seam line is straighter and much less likely to wander. It feels different to the generic foot when I hold it, a little weightier (although only 2 grammes greater in weight) and more smoothly manufactured. It was definitely a false economy buying the generic one but you live and learn. I bought a Bernina walking foot a while back and whilst I got it on offer it was still a significant amount of money but it is amazing to sew knits and bulky fabrics with and I've always been glad that I sold some of my stash and splashed out. It's hard to beat the real thing!
What's your experience with generic sewing machine parts? I remember buying the generic plastic bobbins for my Janome and even they seem to wind slightly differently to the real thing.