Hi guys!
Sorry for the delayed response to this post.
I’d first like to clarify that widgets that are nested inside another dynamic panel cannot push/pull widgets outside of the parent panel. The push/pull only works for the widgets that are in that nested state. This behavior is the same as in Axure RP 8, and the way to push/pull widgets that are outside of the nested panel is to use the “sandwich” method, i.e. hide the outer panel with pull, show/hide/toggle the target, then show the outer panel with push. This will make the push/pull account for the updated height of the parent panel so that the IX works to push widgets outside of the nested panel. I’ve attached an example file to demonstrate this - lmk if you guys have any questions. 
PushPullwithNestedDPs.rp (63.7 KB)
Second, I haven’t seen any noticeable lag with push/pull interactions in the 9 beta compared to Axure RP 8. @plorence, could you post an example .rp file where you’re seeing the slowness?
Last, @kileyjane, I see the same thing with push/pull for showing/hiding widgets inside repeaters in the 9 beta as in Axure RP 8. Here’s an example I just built:
PushPullinRepeater.rp (51.5 KB)
If that’s different from what you’re seeing, or if I misunderstood, could you post your .rp file so that I could further investigate? Thanks!