I have a Kenmore ZZ machine bought new in 1961 that had the tension from he!!. That being said, I made many things on it that turned out well. Just had to check the tension occasionally. If it got 'off', it was hard to readjust. I haven't seen the machine since 1993. It is hiding in one of my sewing rooms.
MW - two - a 15 clone that sews a very straight, strong seam, though it does occasionally need the tension adjusted for no reason. It's very pretty with shamrocks. The second is a plastic machine - probably 70s that has cams and does a great job. It came w/o a bobbin case, but a generic one works fine. $13 for the machine, $13 for the bobbin case, so a good investment, though I don't need it.