Great thread.
I don't have much experience to add except that if you fly an aeroplane equipped with glass (G1000 or Aspen style) it is really worth practicing the scan on standby instruments before you need to do it in anger. Often the analog instruments are placed in a shotgun arrangement all over the panel wherever they'll fit.
I once had an Aspen drop out in the clag before needing to fly an NDB approach to the minima. Thankfully, I was proficient on the standby scan or it would have really got the blood pumping.