I always find the "there hasn't been a mid-air in IMC....." argument to be a bit tenuous. I prefer to consider how many mid-airs there have been in Class G and then try to ascertain the overall risk. It is fair to say that mid-airs in VMC have largely occurred due to failure of lookout - one could assume that being stuck in a cloud is the equivalent of failing to lookout, to a far greater degree. Consequently the counter-variable has to be related to the reduced number of pilots floating around in IMC compared to those operating in VMC.
So, if you subscribe to the big sky small number theory, crack on. Alternatively, mitigate with a radar service or steer clear of cloud.
As Dirty Harry would say, "Do you feel lucky, punk?"
PS. How many 'airprox' have there been where pilots don't even know it has happened? Donald Rumsfeld would describe this as the "unknown, unknowns".