The entity list makes quite heavy use of bindings and UI panels, so it naturally highlighted a bunch of performance issues within the UI layout system.
I spent a day optimizing a few benchmarks I threw together, with 10,000 panels, and managed to get it performing on average about 6x faster.
This isn't the end of this, I've just managed to make the performance less embarrassing. I think we can make things a bit more threaded to improve things further - but don't want to do that until I have to.
