I have been working with Entities since 0.0.12, and usually new updates meant both bug fixes and improvements. But more recently we began to struggle with the updates. In Entities 0.9-0.10, we had a lot of problems with IComponentData classes as well as component objects in the EntityDebugger. To a point where too many errors were thrown at runtime, only in a build. Errors causing the game to not respond or to break entirely. Things like Transform or TMPro being stored in component data class caused a lot of problems, problems difficult to pinpoint and resolve. In Entities 0.11, it is no longer supported to have ComponentSystemGroup with OnCreate methods without calling base.OnCreate. That's a first in Unity. Never did we have to call base.OnUpdate, base.OnStartRunning or anything like that, but now it is the case with ComponentSystemGroup. My point here is: Why add the possibility to use classes as IComponentData if even built-in components can't be stored in them safely? And why changing things so fundamental as to require base.OnCreate in all ComponentSystemGroup? Wouldn't it be best to stick to what works, or maybe to have a stable vs preview versions of the package? It is rather surprising that we never ran into such issues with earlier versions such as from 0.12 through 0.9. Upgrading was always a breeze and brought many improvements. But now it is becoming a real nightmare to upgrade. We of course love the direction of DOTS, just not these few hiccups. Cheers!