I've been using UltraFlex JetFlex 13oz for about 2 years. I've only ever had one bad roll (about 2 weeks ago) but that was caused by "improper storage" and Fellers replaced it.
I'd still recommend the JetFlex to anyone.
I've also used Key banner from Grimco but didn't care for it. To me it felt "brittle", that may be because it was a matt finish and I'm used to glossy JetFlex. Still didn't care for it.