Everyone over designs project management systems. They end up not being used, or used marginally with only the minimal features. Plus they waste tons of time simply by being confusing. Although I've not used Open Atrium, I've looked into others and found them lacking. Seriously, terribly lacking.
I've had great success with the following zero-budget solution:
1) Use the Node Comments module to promote comments to full nodes.
2) Use CCK to make your comment Content Type contain additional fields, such as "start time", "end time", "time worked", "supported by [team members]" and so on.
3) Each "Project" is simply a Page with the project description. Each comment is someone's contribution to the project, with any tracking fields you cared to add to the comment Content Type.
4) Additional "reporting" logic in a custom module that looks at these "time record" comments and generates useful aggregate summaries.
Total time to get system working: 1 day.
Total time to get company using system: same fricking day!
Feeling of control over their environment by client company: total.