At the Pervasive Computing area, end users expect to receive a multimedia service with an acceptable quality, anytime, and anywhere. Measuring this acceptability is usually referred to Quality of Experience (QoE). Unlike Quality of Service (QoS) which focuses on allocating expected systems and network resources, QoE is concerned with optimizing the perceived quality of a service by end-users. The appraisal of the user's acceptability thresholds is a key factor for service providers to perform adaptation decisions on their products (VoD, IPTV, online games, etc). While QoE is individualized, no study has yet examined to what extent. In this paper, we report an empirical study to understand if QoE should be managed globally, per cluster of users, or personally. We prove that every user has his very own vision of a same service, therefore that future QoE-based adaptive systems should take into account this property.