Predicting the user Quality-of-Experience (QoE) for an internet application is a highly desirable feature in a number of situations. However, directly measuring user QoE is extremely challenging, due to its subjective nature. One common approach is to measure Quality-of-Service (QoS) metrics and use it to predict user QoE. In this presentation, we show our efforts into understanding and predicting user QoE. First, we will discuss state-of-the-art quality assessment methodologies. Then, we will present several approaches to model user QoE from QoS metrics. Finally, we show a few examples where we model user QoE from QoS metrics.