In a mobile computing environment, an end user?s experience can be degraded due to changing runtime conditions such as: high and very variable network latencies, server overloading caused by a large number of devices accessing a shared resource, inconsistent experience on different devices as mobile devices vary in resource capabilities, and service disruptions due to the lack of the network, a server or a device. In this paper we present the Agile Operating Environment (AOE) that improves on a users experience by enabling on-device service replication, fault tolerance, and dynamic user interface presentation binding. An important aspect of these three features is that they adapt to runtime conditions to further improve the end users experience. We have prototyped the AOE system and several applications. In our design and in our prototype we have tried to adhere to the model of web application in order to enable easy application portability. Our results demonstrate that our adaptation techniques can significantly improve a users experience by reducing the degradation that is typically evident in a mobile environment.