The BEST way to evaluate the effectiveness of a newly developed application is to:

The best way to evaluate the effectiveness of a newly developed application is to review acceptance testing results. Acceptance testing is a process of verifying that the application meets the specified requirements and expectations of the users and stakeholders. Acceptance testing results can provide evidence of the functionality, usability, reliability, performance, security and quality of the application.Performing a post-implementation review, analyzing load testing results, and performing a secure code review are also important activities for evaluating an application, but they are not as comprehensive or conclusive as acceptance testing results.

References: Info Technology & Systems Resources | COBIT, Risk, Governance … - ISACA, IT Governance and Process Maturity