Almost all the major ways in which NT deviates from UNIX have strong cases as being architectural wins:

- A well-defined HAL for portability

- An object manager for unified resource lifecycle and governance

- Asynchronous I/O by default

- User-facing APIs bundled into independent “personalities” and decoupled from the kernel

The only real black mark I’m aware of is the move of the graphics subsystem into the kernel for performance, which I don’t think was Cutler’s idea.