Putting the performance complaints aside - one other thing that is essential IMO is feature-parity with PhysX, which Chaos still does not have despite the documentation stating otherwise. That concerns me somewhat.
Ideally we also really need this more advanced stuff more easily exposed, as using some of these features is very difficult in UE4, because of the abstraction layer between UE and the Physics Engine and all the translation that occurs between them (which also adds it’s own overhead).
I was hoping that Chaos would see that abstraction layer removed eventually - though I understand that would make it difficult to integrate another physics engine.
A couple of missing items such as contact modifiers and backface queries I commented on here. These are essential features for some of our gameplay systems, such as bullet penetration for example. Missing features and performance make Chaos unusable for us currently.