I am evaluating your product. In our application we use custom collections rather than datasets. Is it possible to use an array list as the data source for the mail merge execute method?
How do you want to map your data to merge field names?
You can achieve mail merge effect yourself by using DocumentBuilder.MoveToMergeField or MoveToBookmark and using other DocumentBuidler methods to insert the data there. If you need to repeat the document or section for each record, then you can use Section.Clone and Sections.Add to make a copy of a section for each new record.