  Many software companies face challenges in their work with User eXperience
(UX) and how to integrate UX practices into existing development processes. A
better understanding of these challenges can help researchers and practitioners
better address them. Existing research does not analyse UX challenges in
relation to other software quality characteristics including usability. In this
empirical study, we have interviewed 17 practitioners from eight software
development companies. Their responses are coded and analysed with thematic
analysis. We report 11 challenges that practitioners face in their work with
UX. Some of these challenges partly overlap with those reported in existing
literature about usability or software quality characteristics. In contrast to
these overlaps, the participants of our study either view many of the
challenges unique to UX, or more severe than for usability or other quality
characteristics. Although at a superficial level challenges with UX and other
quality characteristics overlap, we differentiate these challenges at a deeper
level through two main aspects of UX: subjectivity and emergent nature. In
particular, we identify at least five issues that are essential to the very
nature of UX, and add at least seven extra difficulties to the work of
practitioners. These difficulties can explain why practitioners perceive the
challenges to be more severe than for other quality characteristics. Our
findings can be useful for researchers in identifying industrially relevant
research areas and for practitioners to learn from empirically investigated
challenges and base their improvement efforts on such knowledge. Investigating
the overlaps can help finding research areas not only for enhancing practice of
UX but also software quality in general. It also makes it easier for
practitioners to spot, better understand as well as find mitigation strategies
for UX challenges.
