I know they are ugly. I've used about every ring and base system made at one time or another but keep coming back to the weaver bases and rings. They just seem to work when nothing else will. I've had them on some heavy kickers without a problem. I did find that you should use the bases with weaver rings not imitators. And the Quad lok rings are lighter than anything on the market.
Do any of you use them and whats your opinion ?

I've used on pretty heavy stuff, not had a failure. Old gunsmith I knew hated the way they looked, liked dovetail type for looks but thought nothing worked better than the Weaver.
I like them.

Great system. I use the Warne rings that fit weaver bases. Remember the same screw hold all bases down.