VERY intersting perspective! Just goes to show just how much actually goes into an airplane.
One thing about the CRJ regarding the APU -
The exhaust port is out the side of the airplane which causes two undesirable effects.
1. It is VERY noisy on the ground, as CrewChief32 pointed out.
2. If the aircraft is pointed white (Comair) the exhaust from the APU leaves a huge black streak across the back of the airplane. Three things would solve this: Don't use APU in the air, not very practicle...move the APU to the stinger of the tail like the CRJ-700 has, again, not practicle...or by simply painting the lower tail a dark color like black or dark blue, that black streak is not visible.
It doesn't detract from the performance of the airplane, but I've heard countless passengers worried because their plane has "been on fire."