The Tiger Initiative has been working on the usability of clinical applications for some time now. They just published a report with recommendations. I know a few of the people involved. It's worth a look. Link
Since 2007, hundreds of volunteers have joined the TIGER Initiative to continue the action steps defined at the Summit. The TIGER Initiative is focused on using informatics tools, principles, theories and practices to enable nurses to make healthcare safer, more effective, efficient, patient-centered, timely and equitable. This goal can only be achieved if such technologies are integrated transparently into nursing practice and education. In order to meet the demands of an increasingly electronic and rapidly changing healthcare environment, it is essential to address the educational needs of the nursing workforce.