I have been upgraded on 43 of 49 eligible flights this year on mainline PMCO flights and although I do believe there have been glitches with the upgrade system over the past few months (such as no upgrades clearing until day of departure when First was almost empty) I believe that for the most part the upgrade system (on PMCO at least) operates as advertised and intended.

I don't mind if someone else gets an upgrade and I don't, as long as there is a reason for it and the rules are applied consistently, so to me transparency and consistency (regardless of the actual rules being applied) are the most important factors in determining my satisfaction with the program. (That and my actual upgrade rate, of course.)