I love my 1973 SU with cams. That machine has sewn everything possible and is still, as Candace says, the quietest around. Not a good quilter because of the self adjusting presser foot, but wonderful at everything else. My children had some trouble with her until they learned to hold the threads when starting to sew. That is Miss Elna's only issue.
Lucky you if you got these at a good price. I have been looking for one for a friend and they have held their value, that's for sure.