CAM is a user interface toolkit that allows a camera-equipped mobile phone to interact with paper documents. It is designed to automate inefficient, paper-intensive information processes in the developing world. In this paper we present a usability evaluation of an application built using CAM for collecting data from microfinance groups in rural India. This application serves an important and immediate need in the microfinance industry. Our quantitative results show that the user interface is efficient, accurate and can quickly be learned by rural users. The results were competitive with an equivalent PC-based UI. Qualitatively, the interface was found easy to use by almost all users. This shows that, with a properly designed user interface, mobile phones can be a preferred platform for many rural computing applications. Voice feedback and numeric data entry were particularly well-received by users. We are conducting a pilot of this application with 400 microfinance groups in India.