To implement seamless mobility inside an integrated, multiple (e.g. GPRS/WiFi) access system, a vertical handover policy has to be devised. This is usually done at the mobile terminal, allowing it to be customized from a end-user perspective, in order to fit individual needs/preferences. We propose a new approach in taking vertical handover decisions, which are not anymore exclusively based on the knowledge of the available access networks' characteristics but also on higher level parameters which fall in the transport and application layers. To this extent, in this paper a model has been realized and simulations have been run in order to evaluate the impact of the vertical handover and its frequency on a set of typical user's network applications/services. We also take into account the user preferences in terms of cost and quality of service. We believe this approach reflects the optimal settings from the user's point of view with regard to his running services and applications. Our aim is to understand how to define a metric to be used in order to devise a solution which should try to balance the overall cost of vertical handovers with the actual benefits they bring to actual user's networking needs. This way, each mobile user could autonomously apply the handover decision policy which is more convenient to his specific needs.