Cross-platform services allow access to information across different devices in different locations and situational contexts. We observed forty-five participants completing tasks while transitioning between a laptop and a mobile phone across different contexts (seated–moving and seated–seated). Findings showed that in each test setting, users were sensitive to the same cross-platform user experience (UX) elements. However, the seated–moving settings generated more issues, for example, more consistency problems. Two moving-related factors (attentiveness and manageability) also affected cross-platform UX. In addition, we found design issues associated with using mobile user interfaces (UIs) while walking. We analyzed the issues and proposed a set of UX design principles for mobile UIs in moving situations, such as reduction and aesthetic simplicity. This suggests designing context-aware cross-platform services that take transitioning into account for enhanced mobility.