I had a client with a C++ application that used COM for everything. They wouldn't write a simple C++ class or structure but rather would always fire up the wizard in Visual Studio to create a COM object. It was horrendous.

Having said that COM itself wasn't that bad. If you read the Don Box book he justifies pretty much all the technical decisions they made.

In the end my productivity doubled when I shifted from C++/COM to C#/.Net.