The main concern of this thesis is finding optimal ways of obtaining information from software users with a special focus on long-term studies on momentary opinion, meaning the short-term opinion that people have at the very moment of asking the questions. I chose the event-contingent protocol of the Experience Sampling Method (ESM) as an efficient methodology for this kind of studies and implemented it in a surveying system called Crowdpinion, which consists of a web panel used by researchers to configure studies and a mobile app for participants of the studies. Long-term ESM studies are in many ways similar to crowdsourced generating of research data and just as the workers in crowdsourcing, the participants in studies need to be motivated in some ways. In this thesis I discuss some motivation factors and describe the gamification elements that I included in Crowdpinion in order to increase participants engagement. Studies on momentary opinion can produce valuable data, which can be combined with results from surveys-based retrospective studies or used separately. Having the data from a momentary Experience Sampling study researchers can learn much more than from retrospective studies. For example, in a classic survey they can ask a question like Did you feel tired at work in last weeks? and obtain responses about what the participants remember about their overall tiredness at work. In an ESM study, the researchers can ask the same question Are you tired now? many times in different situations over long time. By doing this, they obtain much more data, which allows them to analyze how the feeling of tiredness changed in different times of a day, in different days and in relation to different events. It is also important that the responses in momentary studies are not biased by memory, because they are reported almost immediately after analyzed events. The scope of studies that can be conducted using Crowdpinion includes evaluation of public services, User Experience, work environment and many other topics.