Many of our customers use Crystal Reports in conjunction with their DevForce apps. Historically, this has involved sourcing the reports directly against the back-end database or against an in-memory DataSet rather than an object model, both of which approaches have the disadvantage of requiring the logic for computed properties to be recreated in the report.
I've been told by attendees at our DevForce classes that Crystal can now report directly off an object model, but I have no first-hand experience of this, and don't know how well it works, what its limitations are, or how performant it is. Two report writers that are definitely object-friendly are XtraReports by Developer Express and ActiveReports by DataDynamics.