Many project management applications either restrict themselves to dealing with only specific aspects of a project's life-cycle (such as task scheduling and monitoring) or have been developed to work best in certain industries. Contrary to this, ]po[ is a highly customizable package that can be tailored to include exactly those processes needed for your organization. When setting up the software, you can choose exactly which components will be visible to users as well as who will have access to each component. However, as your business needs grow, you can easily activate and include other modules of the software and expand the application's capabilities without having to start from scratch.
For one comparison, I've long been a fan of dotProject as a PM solution for small to mid-sized businesses. However, with a bit of growth, it doesn't take long for these businesses to realize that they need something in addition to dotProject, especially when they want to keep more detailed financial records or incorporate an issue-tracking system. With ]po[, you can have all the functionality of dotProject during the early stages of your business and expand to include other capabilities, if and when you need them.