Works for me…even 95% overcast with a few holes and the ability to roughly make out something that looks like trees or a field in said hole. :-)
Peter – whilst I have a very nice IFR aircraft and fly IMC when necessary (legally I hasten to add) your picture looks very forbidding to me. My experiences tell me not to venture into something so very dark!
On photos, the weather tends to look much worse than it is in reality.
There were buildups from about 2000ft to about 8000ft, no strikes, some rain, temperature at that level (5000ft or so) was +6C so no icing risk. I flew it very slowly, 120kt (Va is 130kt or so). Quite a lot of turbulence in the clouds but not enough to disconnect the autopilot.
But more importantly I could see, from further back, the general “layout” ahead, so this stuff was known to be a temporary thing. Also I had a radar image
which confirmed it. The photo was taken around GWC (Goodwood) so you can see it is just a narrow stripe of muck.
I would never fly in solid IMC for any significant distance (e.g. more than the width of one cloud) without some peripheral information on what might be lurking in it.
That flight was 100% legal – Class G and I have an IR, etc. My post was tongue in cheek, taking the p*ss out of the long standing UK rule (ended April 2012 for JAA issued PPLs) requiring sight of surface for VFR.
Here is another one
If I can see a tip of a hill/mountain anywhere on the horizon I am in sight of suface 
