I'd like to know what view finder settings are preferred by anyone out there with their F3. By default the settings are:

Backlight: High
Mode: Color
Contrast: 0
Brightness: 0
Power: Auto

For a while I've had the brightness and contrast risen to around +44 because what appeared in the view finder seemed to match the environment, but now when using s-log I'm not so sure.

On a related matter, what does 'MF assist' do on the F3?

You should use the colour bars to calibrate the LCD and viewfinder. Use the contrast adjustment so that with the colour bars on, the 100% square white reaches maximum brightness and appears white without blooming or looking overly bright. This should be the point where as you increase the contrast level the white square stops getting brighter. Reduce the contrast adjustment a little until you just perceive the tiniest drop in brightness. Then using the brightness control adjust the brightness so that you can see the pluge bars correctly. See the attached image. There are 3 pluge bars each spaced apart by a black bar. They are at the bottom of the attached image and marked -2%, +2% and +4%. Using the brightness control adjust the brightness so that you can no longer see the -2% (blacker than black) bar but can only just see the +2% bar, the +4% bar should also be visible. Then check the contrast setting again and brightness setting again until you have them both set correctly.