I tie my mainline to the ring that the assist hook is attached to. I have notice a few jigs I have purchased lately have a ring that has been punched out and therefore has quite sharp edges which will need changing. Was just thinking do others tie off to this ring? Or do you use a game swivel or something else? Or do I tie off to the jig or split ring instead (Which would be a pain in the arse to swap jigs out in a hurry)

I came here to say JigStar ring and grommet but it looks like ChrisW beat me to it...

How I think of it is that when you have a fish on it is a straight pull from the hook and trace up through the main line.
Once the fish is on the jig is isolated.

I do use a game clip but the same thing applies.