I'm excited about new native interop api (function pointers, UnmanagedCallersOnlyAttribute, etc.). It removes "managed code tax" for calling into dynamically loaded OpenGL/Vulkan methods from c#.

I'm playing around with GLFW via PInvoke, which meant marshalling openGL function pointers into managed delegates. In net5.0 preview, I can simply cast IntPtr into a function pointer, and boy, a call to your average openGL method is literally an order of magnitude faster.

Similar optimizations might have been technically possible before, but it required some icky bytecode tinkering.