In the demo app (or any app using this code) some leaks appear in Instruments / Activity when you resize the window.
(Looks like the code allocs a LOT of cells on resize, without queuing / dequeuing and do not throw them away)
I ran into this myself. It appears to be the _cellYOffsets array that is allocated in PXListView's cacheCellLayout, but only freed in reloadData. cacheCellLayout is called from a number of places, but the only time the array needs to be reallocated is in reloadData. I moved the allocation to reloadData, just before the call to cacheCellLayout.