Oddly, we didn't have much in the way of wheel slip problems. Our issue was we couldn't run them wide open up the hill because of the 10mph speed limit. The drag speed was about 18 mph, and if you loaded it down to run wide open at 10 mph, you were deep in the short term loading.
The GE's were expensive to keep running. Compared to EMD's, the parts were about 50% higher and IPH bought about $20k in specialized tools to work on them. The CMO at the time knew nothing of GE's, so they sent one of his underlings to "GE School" to learn about them. He later got fired.
The best thing they did was barf up big clouds of black smoke and flames when you wound them up leaving town...... I could stop traffic on US 160 west of ALA when I cleared the Yard Limit headed to Monte Vista.
At least they kept the mosquito down...