I've bought upper wishbones from these people (as in the OPs link) and fitted them with no problems so far.
My logic in buying non-original was that the originals had done less than 30,000 miles and were squaking like mad, so let's see what non-originals can do at half(?) the price.
So far, six months in and 10,000 miles covered, no problem . . . Don't see the harm in trying them. If they only last another 10,000 miles then I'd still consider buying non-original - but then again, I DO fit them myself.