Geoff Wilson is probably the worlds best knot guy and I believe what he says. His fishing experience alone dwarf's most everyone I know. He says it is a 90% knot. I believe him and my results mirror its effectiveness. For trout flies most of the time you want a straight connection anyway, especially for dry flies. It is too easy to break 4 lb that an unscientific pull test using your hands means nothing.
One must also take into account that knots are not meant to be an all day affair. After each good fish you better retie and sharpen your hooks. It you do not you are only asking for trouble. Nowhere was this more apparent than earlier this season on the canal. Basser caught what was over a 40" fish. He eas using a slim beauty for his mono to braid connection on his spinning rig. The fish put up a good fight in the heavy canal current and was landed just fine. Next cast he hung up and the knot popped while he was barely applying pressure to try and free the hook. All knots loose effectiveness after being stretched by fish. You should have retied those knots,any number of them will fail after repeated strain.