Agile Requirements Engineering (Agile RE) has been widely studied, but gaps remain regarding how user-centered research practices, specifically UX Research, are integrated into Agile RE. This paper investigates how UX Research is applied within Agile RE activities and identifies the positive and negative aspects of this integration. We conducted a multiple-case study with four distinct organizations, collecting data through interviews with 12 agile and UX professionals. Our results revealed that UX Research practices and tools are most frequently employed to discover requirements, both in organizations with and without UX professionals. However, the findings also indicate that although UX Research practices provide valuable input for requirements specification, there remains a need to better structure and communicate UX-related aspects so they become more visible to the agile team in all Agile RE activities. Our study contributes by discussing how UX Research practices and tools are employed across the stages of the Agile RE cycle, as well as the roles of the different stakeholders involved in these stages in different companies.