Just on interiors... what REALLY drives me up to the wall with regards to Ford/GM is the plastics and switch gear they use.
The dash, door trims, etc all feel.... hard. I've not been in a cadillac (they pretty much don't exist here) though.
Ditto for the switch gear. Every time I drive a GM or Ford, It feels like it is going to break. The way the levers click into each detent etc just feels cheap. I know this sounds really petty, but on my E39, the levers for indicators, wipers, shifter, etc. all just feel ... right.
Ditto for steering weight, steering wheel feel, pedal weight, etc.
Also when replacing light bulbs... all the retention mechanisms have the same feel of solidarity and precision.
You know that feeling you get when you hop in a car and it all just feels "right"? That's it.
I hop in a lot of other cars and the steering feels wrong, pedals feel wrong, driving position feels wrong, brake pedal sensitivity/pressure feels wrong, etc, etc - and you need to "Get used to it".
Now don't get me wrong. The E39 breaks a lot
It makes me want to cry sometimes. But damn i like driving it...
edit:
Example - VANOS seals. beemer owners will know what I'm talking about. High tech VVT system that is well engineered.... crippled by crappy rubber oil seals that degrade over time when exposed to oil.
Cost to fix? say $2.5k...