Hmmmm .... interesting ....

To me, its very simple .. understanding!
U have to understand what the computer is doing for u.
What is it calculating.
What is RGBM (for Suunto users).
What limiting factor does it have.
What function does it have.
What are they trying to tell you underwater for each beep and each blink.
Once u understand all that, then u decide for yourself how much can u rely on it. They dont manufacture it to be useless underwater rite?
Dont buy PDC just because everybody else is using one and to look cool to others. Get it for the function that they capable of giving u. And most importantly, only get a dive computer only after u have fully understand your dive table.
And once u get it, maintain it properly ... check the battery level every now and then, or better before every dive (i do that even up to today). Only send it to a certified technician, even for battery replacement. Or even better get yourself trained as how to maintain it.
I know for a fact that Suunto dont allow just anybody to tamper with the electronics in the PDC. Should the display is showing anything that it shouldnt or not showing anything that it should, then the rule is to send it back to the factory in Finland. No other company/person in the world is certified to tamper with the electronics inside.
With all that in mind, u can decide for yourself how much can u rely on your dive computer.