The GPS in a mobile device is power hungry.
Weather a user experiences any difference will depend on weather other apps they use also use location services. If they did the user wont notice any difference. If they didn't then they now have something extra turned on using power that they did not have on before.
Amongst my clients I haven't had anyone report any difference in their battery lifetime,
I guess this will depend a lot on the device. Take Android for example, it will automatically remove CPU time from apps not used frequently, but differnt manufacturers use different triggers for this. Often the triggers are related to how much battery the device currently has.
