If you read Don Box’s book on COM he goes through every decision they made and the rationale for it. It all seemed to make sense.

Unfortunately I think Don Box’s was the only person in the world who really understood it all.

As idea it is great, as the tooling available in C++ Builder, Delphi, VB 6, C++/CX (WinRT is basically COM with extras) also great.

Using it from MFC, kind of alright.

Using it from .NET, depends if Framework, .NET Native, or modern, with various levels of usability.

Using it from ATL, WRL, C++/WinRT, is a mess unfortunely.