The datasheet view has always been a great asset to document libraries. It was really easy to change the value of multiple documents instead of editing every single document separately. If you upload multiple documents in a document library with custom metadata, SharePoint never asks to assign custom metadata to the documents. This means that you have to edit every single document or use the datasheet view. New to SharePoint 2010 was the term store with its taxonomy features. To use a taxonomy within a library you had to use a managed metadata column. This column wasn’t supported in the datasheet view in SharePoint 2010!