With reference to the General Packet Radio Service (GPRS), an extension of the Global System Mobile Communication (GSM) addressing packet-oriented traffic, this paper contributes to the analysis on the service accomplishment level perceived by GPRS users. The proposed modeling approach builds separately the GPRS and user models; the focus is on the GPRS access random procedure on one side, and different classes of users behavior on the other side. The overall model is obtained composing the basic submodels. Quantitative analysis, performed using a simulation approach, is carried out, showing the impact of users characteristics and network load on identified indicators expressing the QoS as perceived by users.