When you click on an attachment in a document, you have the options to open or edit the attachment. Wherever you click, the attachment will open/edit in the same application. It would be nice if the application that open an attachment for reading is configurable.
So, by example, i can open an attachment for reading with the free MS Office Viewer, downloadable from Microsoft Web Site, and open the same attachment in OpenOffice or Symphony for editing.
I think, a migration from Microsoft Office to OpenOffice or Symphony would be easier, if you have the Opportunity to view and print Office Documents in his originally look, as they would look like in MS Office.