Socially interactive robots are expected to have an increasing importance in everyday life for a growing number of people, but negative user experience (UX) can entail reluctance to use robots. Positive user experience underpins proliferation of socially interactive robots. Therefore, it is essential for robot developers to put serious efforts to attain social robots that the users experience as positive. In current human-robot interaction (HRI) research, user experience is reckoned to be important and is used as an argument for stating that something is positive. However, the notion of user experience is noticeably often taken for granted and is neither described nor problematized. By recognizing the complexity of user experience the intended contributions can be even more valuable. Another trend in HRI research is to focus on user experience evaluation and examination of user experience. The current research paths of user experience of socially interactive robots are not enough. This chapter suggests that additional research directions are needed in order accomplish long-term, wide-spread success of socially interactive robots.