My biggest complaint right now is the occasional lag in navigating between menus, acknowledging safety disclaimers, etc but it's more than tolerable IMO.
There's the rub--"tolerable" and how that might translate into a CR rating.
For example, I'm quite happy with my $125 Garmin with lifetime map updates. It fires up and finds satellites pretty quickly, usually a matter of a few seconds. It probably has a 5 year life span before the internal battery gives out. It goes pretty quickly into recalc mode if I go off route. It flips instaneneously between the map and the turn-by-turn descriptions. It's rare for it to drop satellite connection. The Garmin goes back and forth between two cars as needed. I cannot recall an instance where my wife and I needed it at the same time. In essence, I'm comparing a $125 item to $800 worth of equivalent in-car tech for my needs.
So, based on that experiece, what if I went out and popped for a $400 Mazda navi or $800 for two and I experienced a "tolerable" performance issue that I did not experience in my Garmin? In short, what if Garmin performance was on-balance superior for my needs and I don't care about the futzing in moving it to the other car, plugging in, stowing, etc.?
Do you think I'd be justified in docking the Mazda system in some way in a review? I think so.
Again, CR does not have a rating scheme for "not broke, but it is what it is" for design shortcomings based on folks reasonable expections from using like systems or products. I think allowing folks lump such issues into "reliability" at their discretion has a simplicity that still captures the essense of the matter.
Of course in-car electronics covers a lot of things. There could be a certain thing that is actually broken more often than the competition which any one individual might not experience in their own vehicle.
CR ratings are far from perfect. One area I would question is how all trims are lumped together. For example, if a very small percentage of sales were of a top of the line turbo, and 10% of those experienced an engine problem it might not show up as a red flag in the ratings. Further, a first year rating does not speak to longevity; it's closer to one of those "initial product quality" ratings.
So, these CR ratings are something to consider in the context of a bigger picture.