Unanticipated Software Evolution (USE) techniques enable developers to easily change any element of the software without being obligated to anticipate and isolate extension points. However, we have not found empirical validations of the impact of USE on development cost and quality. In this work, we design and execute an experiment for USE, in order to compare its resulting metrics — time, lines of code, test coverage and complexity — using OO systems as baseline. 30 undergraduate students were subjects in this experiment. The results suggest that USE has significant impact on the lines of code and complexity metrics, reducing the amount of lines changed and the McCabe cyclomatic complexity on software evolution.