here are some faults with different brands
rheem, still mad about the condenser motors hung on cables, and buy some screws with 5/16 heads on them.
carrier, quit stamping your furnace cabinets out of beer cans, short fat furnaces are not a good thing. who designed the duel fuel package, york did away with that design years ago.
york, good ideas, over engineered, how about a little more room in the control cabinet.
trane, how about making sure all your wiring harnesses are plugged in tight, and if you are going to use cheap capacitors, quit mounting them on their side where they will leak.
lennox, how about transfering the qualities of the l series commercial equipment to the residential line.
goodman, how about reeling in your distributors, if they have to load the unit in the trunk of the car, they probably shouldn't be selling it. hacks are killing your reputation.
i could go on but why?