No real problems Steve.
As a kid, GG-1s tended to derail for me a bit (coming off turns the pilots twist down on the outside then ride up the inside straight, but they were the kings of pulling.
I bought the MPC to satisfy my want of an old one at a lower price. The K-line came with the deal.
I didn't see enough difference, from MPC to PW, performance to $, for a just runner.
Both low hour motors in hand, I found the K-line smoother on the track, pulling less amps, less "jack rabbiting", and looked better.
Later, being asked to sell one, I kept the K-line.
I have ran lots of GG-1s though I've only owned a few.
I'm not a lover of can motors. My K-line GG-1 is an exception.
I'd say the most common GG issues of any mfg, would be pilot tracking from them getting tweaked, and pilots falling out of the guide slot while you lift the train. Its like a puzzle. It may pop right back in, or you may have to disassemble them a bit.
You can usually re-tweak them if they bend. Ease, "is a case, by case" thing though.
Kris, It would depend on the question, the Electrical, or Hi rail section would be a good place to carry this conversation to, unless we can figure out a way to work a control system into this, it might be more "polite" to take this over to there.
Maybe post a link here?