We were asked to build four separate departmental websites for UCLA's Fielding School of Public Health. All the sites were running on an old version of Drupal and, when a couple of them were hacked, the stakeholders decided to move the sites to a more secure content management system.
The main challenge on this project was the sheer volume of content that needed to be migrated. In addition, there were a number of user experience issues on all the sites that we had to address as part of the process. Finally, we were required to use a content management system we were unfamiliar with called Open ACS.
This project took approximately four months to complete. We worked closely with the development staff at UCLA who were more familiar with Open ACS and the sites in general. By syncing our efforts, we were able to migrate all the content within about 3 months which gave us an additional month to fix any remaining issues.