In recent years, it has been realized that the success of multimedia services or applications relies on the analysis of the entire user experience (UX). The relevance of this paradigm ranges from IPTV to video-on-demand systems o ering professional TV and user-generated content that is consumed and produced ubiquitously. To obtain a pleasurable and ubiquitous user experience a large amount of aspects have to be taken into account. Major challenges in this context include the identi cation of relevant UX factors and the quanti cation of their inuence on Quality of Experience (QoE). In the particular scenario of ubiquitous production and consumption of content, context awareness and assessment of users' expectations play an essential role. This is further justi ed by the emergence of new multimedia enhancement techniques, notably 3DTV and Free Viewpoint. In the support of ubiquitous QoE the acquired knowledge on the context and on identi ed parameters a ecting users' experience could be used to improve mutimedia applications and their associated content delivery mechanisms.