PiperBoy
You are a good IMC pilot when it takes so little effort to fly IMC in cloud that you can fly instruments while thinking about what you are going to be doing with the wife and family at the weekend or where your tension levels are the same in or out of cloud.
You should be so comfortable flying instruments that it takes up so little of your brain power to do so that you can multi task in the cockpit.
at that point a failure of anything is easier to deal with than if your IMC flying starts as a tense situation requiring a lot of effort at best of times and any failure or problem then builds on that tense background to your IMC flying
As for Hard IMC do you mean cloud bases at or near the minima for an instrument approach ? The fact that you do not get on top for the whole duration or that you are challenged by weather while flying in IMC?
Pace