I just got three gun slides and barrels cerakoted, two that were scratched (G23 Gen4 and XDM 3.8 compact) and one that just had a terrible factory finish (Kel Tec P3AT Gen 2). I just got them yesterday and have yet to test them. What I did notice is that the oil just practically beads up on the surface instead of staying put. The other thing that happened is that initially the guns seemed gritty. Some of the cerakote rubbed off in the rails as would be expected, but unexpectedly hindered the smoothness of racking the slides.
So I lubed each with grease and oil, racked the slides repeatedly and then stripped and cleaned the rails. Quite a bit of black attached itself to the Q-tips. I repeated the above procedures using liberal amounts of lube each time for about 4-5 times per gun. Finally, the grittiness went away and the smoothness returned. The slide rails began to show silver, i.e. removal of the cerakote. That didn't bother me. What did bother me was that the cerakote particals seemed to act like sand, instead of molybdenum (i.e. lubing particals) of duracoat wear. Not good. So it is important to me to get out the loose particals before I shoot these guns. I seem to have done that, but will clean each once again before my first range trip back with them.
I can't tell you how durable cerakote is yet, but I can tell you that as with every aftermarket coating, it isn't perfect. After some time and successive malfunction-free rounds later, I will feel better. Right now, the jury is still out, as it would be no matter what.