PCM scares me because of the fact that it masks problems. You can have a small problem in your setup that keeps getting worse, lets say a component in a servo that's going bad, and you will NEVER know until it gets bad enough that your radio LOCKS OUT and goes into "Failsafe" and you watch your failsafed neutral controls and idle engine fly your plane into the ground. IPD lets the significant problems show through, sort of like PPM, but without a lockout. It's kind of hard to explain, but it works well.

BTW.. my only radio failure was a TX also... I caught it before I took off because I do a range check EVERY TIME I FLY.