Felix von Reischach investigated in his PhD mobile product review systems. The paper  he presented at mobile HCI 2010 in Lisbon compares different modalities for product reviews and recommendations. In particular we looked at the following modalities: discrete scale (stars), text, and video. In a study at the SAP retail lab we compared how easy it was for participants to create reviews in each of the modalities and how much they like creating these. Additionally we also compared which modalities are most liked by people in a buying situation and which type of review the trust. Interestingly a star rating scheme is most liked - for input and output.
Our general recommendation is to allow users to rate products on a scale (e.g. using stars) in different, potentially user defined categories. For a more detailed discussion see the paper .
The evening event of was at Palácio da Pena, Sintra - a castle close to Lisbon. The view and the food were magnificent - it felt like a real treat after the one hour walk up the steep hill.
 von Reischach, F., Dubach, E., Michahelles, F., and Schmidt, A. 2010. An evaluation of product review modalities for mobile phones. In Proceedings of the 12th international Conference on Human Computer interaction with Mobile Devices and Services (Lisbon, Portugal, September 07 - 10, 2010). MobileHCI '10. ACM, New York, NY, 199-208. DOI= http://doi.acm.org/10.1145/1851600.1851635
Research has shown that product reviews on the Internet not only support consumers when shopping, but also lead to increased sales for retailers. Recent approaches successfully use smart phones to directly relate products (e.g. via barcode or RFID) to corresponding reviews, making these available to consumers on the go. However, it is unknown what modality (star ratings/text/video) users consider useful for creating reviews and using reviews on their mobile phone, and how the preferred modalities are different from those on the Web. To shed light on this we conduct two experiments, one of them in a quasi-realistic shopping environment. The results indicate that, in contrast to the known approaches, stars and pre-structured text blocks should be implemented on mobile phones rather than long texts and videos. Users prefer less and rather well-aggregated product information while on the go. This accounts both for entering and, surprisingly, also for using product reviews.