Interesting thread. I have three ME Supers, one was my Father's and it needs work. The other two, one silver one black, work perfectly. With the winder they are a delight to use, although the shutter speed selection in manual I find clumsy.
I also have three MXs, two in silver one in black. One won't meter at all, I'll probably use it as a parts camera. One of the other two I bought used easily 20 years ago; it worked perfectly until it decided to eat meter cells about 4 years ago, devouring them in a month or two. Two stays with a local Atlanta service shop (which shall remain nameless) did nothing except eat my money. The other I bought perhaps a year ago, it too has an appetite for cells. I've taken off the base plate to check for the meter switch actuated by the shutter, it does open. I guess its off to Erick.
I like the handling of the MX, but the shutter speed wheels on mine are stiff enough to make changing at eye level difficult. Other than that it is delightful, excellent meter - when the cells are fresh! - and with the winder just enough extra mass and size for my hands. Good to have DOF preview, why that was left off the MEs I'll always wonder. Should have been a simple addition....