I'm not sure that I will grow it again, but you have to get these things out of your system, and now I've done that.

Regarding washing, it took ages and it's still not totally saponin free, although soaking for a few hours before cooking (a la GA) does make it palatable. Coincidentally Lidl had some fine mesh bags for sale meant for washing delicate items which worked very well for washing quinoa. But it took ages, at least 5 cool wash and rinse cycle in the washing machine.
Oh, don't believe the "theory" that the saponins deter birds. While I was sitting in the barn threshing the seed out into a pail, our resident robin was constantly circling the floor picking up the seed that had prematurely fallen out.
So been there, done that, and hopefully learnt by it.