We address current research concerning patterns dedicated to enable higher reusability during the automated development of GUI systems. User interface patterns are promising artifacts for improvements in this regard. Both general models for abstractions of graphical user interfaces and user interface pattern based concepts such as potential notations and model-based processes are considered. On that basis, the present limitations and potentials surrounding user interface patterns are to be investigated. We elaborate what theoretical implications emerge from user interface patterns applied for reuse and automation within user interface transformation steps. For this purpose, formal descriptions of user interface patterns are necessary. We analyze the capabilities of the mature XML-based user interface description languages UIML and UsiXML to express user interface patterns. Additionally, we experimentally investigate and analyze strengths and weaknesses of two general transformation approaches to derive practical implications of user interface patterns. As a result, we develop suggestions on how to apply positive effects of user interface patterns for the development of pattern-based graphical user interfaces.