SharePoint 2007 has some cool features like blogs, forums, wikis, RSS news feeds, polls, surveys, issue tracking and much more. Drupal is a flexible and extensible CMS which is adopted by corporate, non profits, media, entertainment and governments such as the white house. When there are trouble bugs, you can debug yourself in Drupal and I am not sure about MS removing all bugs. In most cases, Drupal seems to be the automatic choice for adoption.

SharePoint 2007

• Most popular high-level enterprise web application platform
• Supports ASP.NET
• Microsoft product integration (only runs on Windows) and file management features; Excellent integration with Microsoft products like Office, Project, Messenger, etc.
• Open & is highly interoperable
• High bandwidth and CPU
• Intranet platform and also a web framework that can power big websites apart from being on the same league with other larger CMS platforms
• Features & functionality: Forums, Communities, blogs, wikis, RSS feeds, news aggregation, surveys, issue tracking, Search, Insights, Composites
• Total Cost of Ownership (TCO): Licensing plus development plus management plus support cost. Subscription and license cost amounts to $13066 (5 users) plus overhead costs (15%)
• SharePoint community has over 17,000 customers, 400 Independent Software Vendors & 4,000+ System Integrators and over 500,000+ developers.
• SharePoint doesn’t work well in non IE browsers
• SharePoint will go awry if your architecture is not in place, otherwise you’ll find duplicate content and resources everywhere
• Getting started with SharePoint is always difficult for first time users

Drupal 7

• Written in PHP
• Open source (CMS) that is extensible & interoperable. It is aimed at web/community solutions
• Free framework, but development & support costs can really increase the TCO
• Supports multiple operating systems
• Drupal development is easy to set up and launching Drupal sites on shared environments requires not much technical knowledge and skills.
• Drupal’s document management functionality and integration with tools like Microsoft Office and OpenOffice is severely lacking
• Drupal has 11000 free modules and Theming is powerful
• Office (open or ms office, doesn’t really matter which) integration, offline documentation creation/editing, automatic office document synchronization and revision control are not possible
• Drupal has 11000 free contributed modules
• A large community of 648,000 users and 10,000 developers
• Drupal suffers on integration with office (open or ms office), create and edit offline documentation, document synchronization and revision control

At present, if there is an open source alternative that offers both document management and web based content management, this is the best bet.