I considered using CFRunLoopSource (there's an aside buried at the end of the readme mentioning that as a future exploration) but it didn't offer a clear enough win on unsafe usage (so far).
As far as questions my experience in the 1:1 labs in the past was that it's better to come in and show the project and point at some of the sharper edges and see what feedback you get but if the forums is better suited to specificity I'd ask for feedback about the usage of pthread specific as a way to hold state for observer callbacks when working against an API (AXObserver) that has no defined safe point to perform cleanup after removing an observer. What I have is working, but it's quite warty.