Angus, I know exactly what you mean. I recently purchased one of the Sears hybrid saws.(It is made by Steel City also) I assembled it and it was dead on accurate, right out of gate. I was able to set the angle at 22.5 deg and made an octagonal box in about 5 minutes and the angles were perfect. So much so, that the box practically fell together by itself.
I got Doug Stowe's Basic Box Making book and his Box Making book. They are both filled with tons of box making info and jigs.
"If it ain't broke, don't fix it, give it to me!"