IMHO, the COM API for Word is hardly worth calling an API. It's written on top of the User Interface instead of providing an API to the underlying Document Model.

For example: you need to activate a document before you can use it, you need to explicitly create a selection to change it, you need to programmaticaly type text to insert anything in a document, etc.

I'd rather use a standalone library like Jakarta POI, than having to launch MSWord to programmaticaly create documents.