I voted for the M4-2. I realize that personal prejudices come to the front in this, but I got a very early M4-2 (traded in my M5) mostly to get the winder. Both camera and winder were huge disappointments. My M4-2 had numerous problems, and died on some rocks after a poorly attached strap eyelet came out. The winder was atrocious.
I had the M5 for about 2 years. The meter was nice, but the cell arm swinging out did not aid the overall feel. The bottom rewind precluded shooting Fuji film at the time, and of course it didn't take the IXMOO cassetttes. I like the overhanging shutter dial, but it felt rather wobbly. Basically, it wasn't fully sorted and obviously didn't have the development time of the M2,3 & 4.
Metering was nice, but not at the expense of handling and film choice. Fortunately I still had a couple of M4's, and kept them until a couple of years after the M6 came out.
The M8 is and has certainly be maligned, but mostly by those who really haven't used one. After nearly 4 years, it's a camera I've been very happy with. I'll keep one even though I have an M9.
Henning