Here at Freelock, we've been making the transition to using Open Atrium as our project management platform, and thus far I've been quite impressed with it. As good portion of my background has been in organizational and project management and I've had the occasion to acquaint myself with a variety of software tools used in that role, John asked that I weigh in on the program.
OpenAtrium is an online collaboration and task-management suite built on top of Drupal. Like Drupal, it is completely modular, so the feature set can be changed and expanded to meet the needs of a wide variety of applications. Out of the box it has support for case management, collaborative document editing, shared blog and microblog, and a variety of user-configurable dashboard views.
The main advantage I see to OA over more traditional PM tools is how well it fosters both collaboration and communication within a team. It's web-based, multi-user, easy-to-use, and can be configured quite easily to allow users very granular access to functions associated with any number of different roles.
We've gone so far as to set our clients up with their own accounts, allowing them to see and contribute to everything from the current outstanding task list and our position relative to completion of a given task or project. Tasks, comments, and change requests are all recorded in the individual project, which both makes record keeping a simple matter of course and makes it substantially easier for new people to come up to speed on a project. And, of course, this leads to a level of transparency that you couldn't hope to match with even the most aggressive of update meeting schedules.
However, out of the box, there are some rather basic project management tools that OA does not offer; the case manager is set up to manage individual, separate tasks and does not support anything in the way of task dependencies, which means that Gantt charts, critical path analysis, forecasting, and anything else relating to managing time constraints has to be handled externally. Internally, we've been looking at ct_plus, which looks quite promising as a way to integrate these features.
The cost involved can vary substantially.
If your organization is already set up and running a Drupal site and you don't need anything customized, OA could be set up very quickly- in this scenario, we'd charge for an hour to do it. Compared to even a single license of MS Project Standard, that saves roughly $300; the difference in ease-of-use also means far lower up-front costs in terms of the time to adopt, making it a pretty clear winner in this case.
If, however, your organization isn't already running a Drupal installation, the cost of maintaining the server and the Drupal stack itself can be substantial. John did a thorough job explaining the importance of keeping your Drupal site and the underlying environment secured; while the software itself is free and open-source, maintaining a web server and a Drupal installation does represent an expenditure.