Personally, COM gives me the heebie-jeebies. I get why it exists and think it's a cool idea. Under the hood it's just RTTI across shared library boundaries, and it's cool that it "just works" with the way that compilers generate vtables from pure virtual base classes.
But hell did it take me awhile to figure out how that worked because it's so poorly documented and auto-magical. Reverse engineering a COM DLL just to find out how the hell it has a stable ABI is not fun.
