It’s often the case for a VSTO developer (add-in developer) to insert the data into a document. VSTO and Word object model is great to achieve this one. If the amount of data being inserted is large then word automation can be slow. I have authored an MSDN article with our colleagues (Ansari, Sarang Datye and Sunil Kumar) at Microsoft that addresses this scenario.
The interesting aspect is this article explains the usage of Open Xml even when the document is open for editing. Here is the link to the complete article.
Special thanks to Eric White for providing his insights and review.