Yeah,
The question was limited to flying over the mountains at night. Of course it has spead to day VFR and IMC conditions. Rightfully so the concerns are largely limited to single engine airplanes under various conditions.
It is all about assessing the risk factor. If the baby needs emergency medical care all of us would fly night, IFR over the Cascades. But when we have choices it becomes another matter. Of course there are the bush pilots who just go out and do it no matter what. That is their calling in life and I applaud their courage which is second to none. For the rest of us...it is different.
I have flown single engine airplanes 20 or 30 miles off shore over the Great Lakes. Didn't scare me nearly as bad as night over mountains. Something about that water that probably is just as dangerous....but it seems less threatening. Even so....I am not going very far off shore again in a single.
I won't fly IFR in my Maule unless the bases below me are 1,000 ft. or so. And although I have done it.....I don't like single engine IFR at night unless I am over pretty decent countryside. The charity for which I volunteer operates a C-206, a Seneca 2, Seneca 3 and a Chieftain. I quit flying the 206 precisely because we operate it day or night IFR no matter the ceiling is beneath the wings. Call me a coward....guess that it fits. Maybe I just feel that my luck bag is about empty.
Most of my general aviation flying has been in the midwest where there are usually good emergency landing spots. I don't think that I would have enjoyed the same amount of flying all those years over mountainous areas. I've flown hundreds of hours of night time in single engine airplanes when the weather was good and the terrian favorable. Like others have said....night flying is great I see it as almost spiritual. But the conditions have to be right for me.
Now...I've taken the Maule to Idaho, Montana, Wyoming, Nevada, Colorado, Utah etc. and once on a 14,300 mile trip around the nation's external borders. I have flown and will fly again into areas where one is just "dead" if the engine quits. But I do it just a few hours now and then. Consider it an adventure. That is a calculated risk, hoping that limited exposure will keep the odds in my favor.
But once again.....no night flying over the mountains for me, except in a dire emergency.
Have fun. Live long and prosper.
bob