Key qualitative research methods are observation of participants, in-depth interviews and focus groups (Flick, 2009). The purpose of participant observation is to collect data on natural behaviors, interviews allow to study personal experience or history. Focus groups are appropriate for analyzing the behaviour of cultural groups or norms. With regard to researching current and desired functionality of iPads, the best method is in-depth interview, since it will allow to focus on issues specific for every user.
Creswell, J.W. (2003). Research design: qualitative, quantitative, and mixed method approaches. SAGE.
Flick, U. (2009). An introduction to qualitative research. SAGE Publications Ltd.