Well, I set up the Grado Me+ late yesterday night, and had time to play just 2 mono albums -
Song For My Father, BLP 4185, New York USA - right away noticed less surface noise than with the stereo cartridge.
The Modern Jazz Quartet, PRLP 160, 10" original from 1953 - there's no magic, record wear from a heavy 1950s needle can't be reversed.
Like porcy62 said, the mono cartridge seems to track the grooves better than the stereo. I noticed that on the much more dynamic Horace Silver album. I'll do some fine tuning tonight.