Dan,
Well not really PTSD, but it annoys the heck out of me when I look in a Singer such as our 338 or 328 and see metal gears, then look at the others that have the same basic design and see plastic gears which break right when you're in the middle of something.
(Been there - done that).
My wife's Bernina 930 has several plastic gears in it, and so far ( it's an 86 model ) there's been no problem with it. But like you said, eventually they fail.
I think we'll pass the 730, I just don't want any more gears to fix.
Joe