I had warranty problem a few times, but not able to use the claim twice due to being on a road trip, and one time it failed to a point that nothing is left to be warrantied (overheat, separation, etc). I just toss the last tire away because I no longer trust it.
Now that I thought about it, it was really more of the installer problem. Just Tire before bankruptcy was using some Chinese valve stem that leaks and lead to a class action lawsuit, and I think I installed mine there on that set with 3/4 failures. I'm happy they went out of businesses, serve them right.
Walmart tires I got at ridiculously low price were the same formula as the General Altimax RT but some different pattern, I emailed General and they say the compound is the same. Walmart sent me some 3 year old stock and to be honest, I would only use it for my own car but not something I buy for others (who knows if they get stranded because of this) to save $30 per tire.
If all you care about is price, I think nobody can beat Walmart.