Forrester Research published two reports on Drupal. A 6-page report on Drupal itself, and a 15-page report that compares blogging platforms (including Drupal). I don't have access to the reports but here is the executive summary that was published on their website:
Last February, Charlene Li, a principal analyst at Forrester, invited me to participate in the screener and information gathering process but I was too busy at that time. It was around the time that the Open Source CMS Summit in Vancouver took place. Fortunately, Bryght was able to answer their questionnaires.
— Dries Buytaert
Dries Buytaert is an Open Source advocate and technology executive. More than 10,000 people are subscribed to his blog. Sign up to have new posts emailed to you or subscribe using RSS. Write to Dries Buytaert at email@example.com.