Today we spent a lot of time figuring out how to update SharePoint 2010 from Standard to Enterprise. The Central Admin has a feature for that but it kept throwing us errors and getting us nowhere.

It appeared to be that the configuration change to alter the license type has to be done by the system account, which has to be the same account that is running the SharePoint Foundation Timer Service. Besides this the account has to be a local admin on the index and all frontend servers in the farm.